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Archive for the ‘Genetics’ Category

Genetics Clinic – University of Iowa Children’s Hospital

Thursday, August 4th, 2016

About Inherited Conditions

Many diseases and disorders are caused by a persons genetic makeup. These include abnormalities in genes that occur randomly or because of environmental exposures. Other genetic factors run in the family and are inherited at birth from one or both parents.

The Division of Medical Genetics, based in the University of Iowa Department of Pediatrics and UI Childrens Hospital, is a comprehensive statewide resource for families and health care professionals.

Our multidisciplinary team provides hospital- and clinic-based medical care for children and adults with genetic conditions. Testing, diagnosis, counseling, and treatment services include:

We understand that genetic diseases and disorders affect families as well as individuals. Our medical team provides the information, support, and follow-up you need to make informed decisions. We will work with your family physician so you will continue to receive the best all-around care as you move forward. We also collaborate with state and federal agencies, educators, researchers, support groups, and others to provide the latest information and treatment options for Iowans and their families.

From Our UI Children's Hospital Specialists

Read more health library articles on pediatric genetics

A new standardized test for infants alerted doctors to Zachs MCAD deficiency, possibly saving his young life.Read more about Zachs story.

Zephan was born with Alagille syndrome and has had many surgeries because of it, but has made giant strides.Read more about Zephans story.

Andrew was growing up a little bit smaller than the rest of his classmates and new tests revealed why.Read more about Andrews story.

Parking: Parking and Wayfinding. Valet Services Available In House Directions: Elevator F, Level 2.

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Genetics Clinic - University of Iowa Children's Hospital

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FlyBook! | Genetics

Thursday, August 4th, 2016

IN this issue of GENETICS we launch FlyBook, which will present the current state of knowledge of the molecular biology, cellular biology, developmental biology, and genetics of the fruit fly Drosophila.

That we commence this project at the end of the journals first century is fitting: it was work on Drosophila that established the genetic basis of Mendels laws of inheritance (leading to Drosophilas first Nobel prize in 1933). In fact, the very first article published in the journal described experiments with Drosophila that established chromosomes as the carriers of hereditary information (watch for a Perspectives article in January commemorating that article).

The prominence of Drosophila in the pantheon of model organisms is undisputed. T. H. Morgan knew that it could serve as a model multicellular organism when he chose it for his path-breaking work early in the last century, and his prescience has been apparent in nearly every issue of GENETICS. In fact, >20% of the 18,000 articles in GENETICS feature Drosophila in the title!

We did not need to be reminded of how similar Drosophilas genes are to those of other organisms (including ours) when complete genome sequences started appearing 15 years ago, but it was heartening to see. Studies of Drosophila will no doubt continue to inform biology for decades to come.

We have acquired an enormous amount of information about the biology of the fruit fly, and have devised innovative experimental approaches for its study. FlyBook aims to make that information and insight accessible to scientists unfamiliar with Drosophila as well as to the seasoned Drosophila researcher.

FlyBook will span the breadth of Drosophila biology in 50 chapters that will appear as review articles in GENETICS, and will also be compiled on a separate FlyBook website. This enables FlyBook to benefit from the established infrastructure of GENETICSits professional preparation and presentation of articles; its indexing, search, and navigation functions; helpful article features unique to GENETICS, such as direct linking of terms to FlyBase; and its outstanding peer editing. GENETICS is a fitting venue for this updated model of a book.

Experts in their fields will write the chapters, which will be edited by a stellar group of scientists serving on the FlyBook Editorial Board. We thank our Section editors and the authors for their selfless service to GENETICS, to the Genetics Society of America (GSA), and to science.

Work on the fruit fly has yielded much insight into neurobiology, so it is fitting that we launch FlyBook with two articles on this subject. In addition, a Commentary by Gerry Rubin sets FlyBook in perspective.

FlyBook continues the GSAs long tradition of supporting, promoting, and presenting model organism research. FlyBook joins Yeastbook (http://www.genetics.org/site/misc/yeastbook.xhtml) as an important resource for the genetics community. We are proud to present in this issue of GENETICS the first two chapters of what we know will be a seminal series of articles.

Section Editors CELL SIGNALING Marek Mlodzik Mount Sinai School of Medicine Jessica E. Treisman New York University School of Medicine

DEVELOPMENT & GROWTH Trudi Schpbach Princeton University Carl S. Thummel University of Utah

ECOLOGY & EVOLUTION Terese Ann Markow University of California, San Diego Trudy F. C. Mackay North Carolina State University

GENE EXPRESSION Brian Oliver NIH Eileen Furlong EMBL

GENOME ORGANIZATION Sue Celniker Lawrence Berkeley National Laboratory Gary Karpen Lawrence Berkeley National Laboratory

METHODS Norbert Perrimon Harvard Medical School Hugo Bellen Baylor College of Medicine

NERVOUS SYSTEM & BEHAVIOR John R. Carlson Yale University James W. Truman HHMI, Janelia Research Campus

REPAIR, RECOMBINATION, & CELL DIVISION R. Scott Hawley Stowers Institute for Medical Research Terry Orr-Weaver MIT

STEM CELLS & GERMLINE Ruth Lehmann NYU School of Medicine, Skirball Institute Allan C. Spradling HHMI

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FlyBook! | Genetics

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PLOS Genetics: A Peer-Reviewed Open-Access Journal

Thursday, August 4th, 2016

01/14/2016

research article

Sensory neuron diversity is required for organisms to decipher complex environmental cues. Qingyun Li and colleagues highlight the importance of the early prepatterning gene regulatory network as a modulator ofsensory organ precursorand terminally differentiated olfactory receptor neurondiversity in Drosophila.

01/20/2016

research article

Telomeres shorten with each cell division and telomere dysfunction is a recognized hallmark of aging. Madalena Carneiro and colleagues show that telomere shortening and DNA damage in key tissues triggers not only local dysfunction but also anticipates the onset of age-associated diseases in other tissues, including cancer.

01/20/2016

research article

The thymic medulla is known to be an essential site for the deletion of auto-reactive T cells. Rumi Satoh and colleagues show thatStat3 meditated signal via EGF-R is required for the postnatal development of thymic medullary regions.

01/21/2016

Viewpoints

Stephanie Dyke and colleagues examine the variation in data use conditions that are based on consent provisions for genomics datasets in research and clinical settings.

Image credit: Duncan Hull, Flickr, CC BY

Image credit: K. Adam Bohnert and Kathleen Gould

Image credit: Hey Paul Studios, Flickr, CC BY

12/23/2015

review

Albino Bacolla and colleagues discuss recent advances on three-stranded (triplex) nucleic acids, with an emphasis on DNARNA and RNARNA interactions.

Image credit: mira66, Flickr, CC BY

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Genetic Counseling Center – Cupertino, CA – MedicineNet

Thursday, August 4th, 2016

Type of Physician: Geneticist, Ph.D.

What is a Geneticist, Ph.D.? A certification by the Board of Medical Genetics; practitioners work in association with a medical specialist, are affiliated with a clinical genetics program, or serve as a consultant to medical and dental specialists.

Specialty: Genetics: Medical (Ph.D.)

Common Name:

* Provider Directory Terms of Use:

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You are prohibited from using, downloading, republishing, selling, duplicating, or "scraping" for commercial or any other purpose whatsoever, the Provider Directory or any of the data listings or other information contained therein, in whole or in part, in any medium whatsoever.

The Provider Directory is provided on an "AS-IS" basis. WebMD disclaims all warranties, either express or implied, including but not limited to the implied warranties of merchantability and fitness for particular purpose. Without limiting the foregoing, WebMD does not warrant or represent that the Provider Directory or any part thereof is accurate or complete. You assume full responsibility for the communications with any Provider you contact through the Provider Directory. WebMD shall in no event be liable to you or to anyone for any decision made or action taken by you in the reliance on information provided in the Provider Directory.

The use of WebMD Provider Directory by any entity or individual to verify the credentials of Providers is prohibited. The database of Provider information which drives WebMD Provider Directory does not contain sufficient information with which to verify Provider credentials under the standards of the Joint Commission on Accreditation of Healthcare Organizations (JCAHO), National Committee for Quality Assurance (NCQA) of the Utilization Review Accreditation Committee (URAC).

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Genetics – NHS Choices

Thursday, August 4th, 2016

Introduction

Genetics is the branch of science that deals with how you inherit physical and behavioural characteristics including medical conditions.

Your genes are a set of instructions for the growth and development of every cell in your body. For example, they determine characteristics such as your blood group and the colour of your eyes and hair.

However, many characteristics aren't due to genes alone environment also plays an important role. For example, children may inherit 'tall genes' from their parents, but if their diet doesn't provide them with the necessary nutrients, they may not grow very tall.

Genes are packaged in bundles called chromosomes. In humans, each cell in the body contains 23 pairs of chromosomes 46 in total.

You inherit one of each pair of chromosomes from your mother and one from your father. This means there are two copies of every gene in each cell, with the exception of the sex chromosomes, X and Y.

The X and Y chromosomes determine the biological sex of a baby. Babies with a Y chromosome (XY) will be male, whereas those without a Y chromosome will be female (XX). This means that males only have one copy of each X chromosome gene, rather than two, and they have a few genes found only on the Y chromosome and play an important role in male development.

Occasionally, individuals inherit more than one sex chromosome. Females with three X chromosomes (XXX) and males with an extra Y (XYY) are normal, and most never know they have an extra chromosome. However, females with one X have a condition known as Turner syndrome, and males with an extra X have Klinefelter syndrome.

The whole set of genes is known as the genome. Humans have about 21,000 genes on their 23 chromosomes, so the human genome contains two copies of those 21,000 (except for those on X and Y in males).

Deoxyribonucleic acid (DNA) is the long molecule found inside chromosomes that stores genetic information. It is tightly coiled into a double helix shape, which looks like a twisted ladder.

Each 'rung' of the ladder is made up of a combination of four chemicals adenine, thymine, cytosine and guanine which are represented as the letters A, T, C and G.

These 'letters' are ordered in particular sequences within your genes and they contain the instructions to make a particular protein, in a particular cell, at a particular time. Proteins are complex chemicals that are the building blocks of the body. For example, keratin is the protein in hair and nails, while haemoglobin is the red protein in blood.

There arearound six billion letters of DNA code within each cell.

As well as determining characteristics such as eye and hair colour, your genes can also directly cause or increase your risk of a wide range of medical conditions.

Although not always the case, many of these conditions occur when a child inherits a specific altered (mutated) version of a particular gene from one or both of their parents.

Examples of conditions directly caused by genetic mutations include:

There are also many conditions that are not directly caused by genetic mutations, but can occur as the result of a combination of an inherited genetic susceptibility and environmental factors, such as a poor diet, smoking and a lack of exercise.

Read more about how genes are inherited.

Genetic testing can be used to find out whether you are carrying a particular genetic mutation that causes a medical condition.

This can be useful for a number of purposes, including diagnosing certain genetic conditions, predicting your likelihood of developing a certain condition and determining if any children you have are at risk of developing an inherited condition.

Testing usually involves taking a blood or tissue sample and analysing the DNA in your cells.

Genetic testing can also be carried to find out if a foetus is likely to be born with a certain genetic condition by extracting and testing a sample of cells from the womb.

Read more about genetic testing and counselling.

The Human Genome Project is an international scientific project that involves thousands of scientists around the world.

The initial project ran from 1990 to 2003. Its objective was to map the immense amount of genetic information found in every human cell.

As well as identifying specific human genes, the Human Genome Project has enabled scientists to gain a better understanding of how certain traits and characteristics are passed on from parents to children.

It has also led to a better understanding of the role of genetics in a number of genetic and inherited conditions.

Page last reviewed: 08/08/2014

Next review due: 08/08/2016

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Genetics - NHS Choices

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Colloquium | Laboratory of Genetics | University of Wisconsin …

Thursday, August 4th, 2016

Genetics Colloquium - Spring 2016

Wednesdays, 3:30 PM, Auditorium (Room 1111) of the Genetics/Biotech Building

Jan 27

Kate O'Connor-Giles, UW-Madison, Dept. of Genetics Genetic Dissection of Synapse Form and Function

Feb 3

Nitin Phadnis, University of Utah (Pool) "Selfish Genes and Speciation in Drosophila"

Feb 10

Nader Sheibani, UW-Madison, Dept. of Ophthalmology & Visual Sciences (Aki Ikeda) "Thrombospondin-1 and Pathogenesis of Diabetic Retinopathy"

Feb 17

Lauren McIntyre, University of Florida (O'Connor-Giles) "Regulation of Gene Expression in Drosophila"

Feb 24

Aaron Hoskins, UW-Madison, Department of Biochemistry (Pelegri) "Mechanisms of pre-Spliceosome Assembly and Dysfunction in Blood Cancers"

March 2

Reid S. Alisch, UW-Madison, Department of Psychiatry (Aki Ikeda) "Defining the Epigenetic Origins of Mental Illness"

March 9

Christopher Bradfield, UW-Madison, Department of Oncology (Pelegri) "Dioxins, Clocks and Oxygen: Prototype Signals of a Nuclear Sensor Family"

March 16

Jean-Michel Ane, UW-Madison, Department of Bacteriology (Pelegri) "Strange bedfellows: symbiotic signaling between land plants and their microbial symbionts"

March 23

Spring Break - No Colloquium

March 30

Jim Cheverud, Loyola University (Payseur) "Context-dependent gene effects on complex traits"

April 6

Alejandro Snchez-Alvarado, Stowers Institute for Medical Research (Skop) "The Reproductive and Developmental Plasticity of Planarians"

April 13

Steve Henikoff, University of Washington (Rupa Sridharan)

April 20

Mark D. Rausher, Duke University (Hittinger)

April 27

John Yin, UW-Madison (Doebley) "The Chemical Origins Of Life (COOL) Project"

May 4

Mike Eisen, University of California-Berkley (Melissa Harrison)

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Genetics News — ScienceDaily

Thursday, August 4th, 2016

Mar. 7, 2016 Sometimes, a nematode worm just needs to take a nap. In fact, its life may depend on it. New research has identified a protein that promotes a sleep-like state in the nematode Caenorhabditis elegans. ... read more Mar. 3, 2016 Researchers have identified a common ancestral gene that enabled the evolution of advanced life over a billion years ... read more Mar. 2, 2016 Scientists have solved the structure of a key protein in HKU1, a coronavirus identified in Hong Kong in 2005 and highly related to SARS and MERS. They believe their findings will guide future ... read more Mar. 2, 2016 A faster, less expensive method has been developed and used to learn the DNA sequence of the male-specific Y chromosome in the gorilla. The research reveals that a male gorilla's Y chromosome is ... read more Mar. 2, 2016 DNA does not always adopt the form of the double helix which is associated with the genetic code; it can also form intricate folds and act as an enzyme: a deoxyribozyme. Scientists have solved the ... read more Mar. 2, 2016 Every cell in our bodies has its proper place, but how do they get there? A research group has discovered the mechanism for a mosaic pattern formation of two different cell types. Their discovery has ... read more Need for Better Characterized Genomes for Clinical Sequencing Mar. 1, 2016 Challenges in benchmarking difficult, but clinically important regions of the genome have been reported. The results underscore the need to extend benchmarking references against which sequencing ... read more Mar. 1, 2016 This is a story about spit. Not just any spit, but the saliva of cyst nematodes, a parasite that literally sucks away billions in profits from soybean and other crops every year. Scientists find how ... read more Mar. 1, 2016 Our innate immune system uses two mechanisms. The first kills foreign bodies within the phagocyte itself. The second kills them outside the cell. Microbiologists have discovered that a social amoeba ... read more Preserved Siberian Moose With the DNA of Ancient Animal Discovered Mar. 1, 2016 Scientists have found preserved moose in Western Siberia that have unique features of DNA structure. This discovery will help determine the origin and path of moose movement in the last few tens of ... read more Female Fertility Is Dependent on Functional Expression of the E3 Ubiquitin Ligase Itch Feb. 29, 2016 Protein ubiquitination is known to result in its proteasomal degradation or to serve as a signal for tissue-specific cellular functions. Here it is reported that mice with a mutant form of the E3 ... read more Cell Biology: Nuclear Export of Opioid Growth Factor Receptor Is CRM1 Dependent Feb. 29, 2016 The opioid growth factor receptor (OGFr) interacts with a specific opioid growth factor ligand (OGF), chemically termed [Met5]-enkephalin, to maintain homeostasis in a wide variety of normal and ... read more Feb. 29, 2016 DNA is made from four nucleosides, each known by its own letter -- A, G, C, and T. However, since the structure of DNA was deciphered in 1953, scientists have discovered several other variants that ... read more Feb. 29, 2016 Microsatellites are a key tool for researchers working to understand the genetic diversity and evolutionary dynamics of organisms. A recent study offers a deeper understanding of the utility and ... read more Watching New Species Evolve in Real Time Feb. 29, 2016 Sometimes evolution proceeds much more rapidly than we might think. Genetic analysis makes it possible to detect the earliest stages of species formation. For example, a new study investigating rapid ... read more Blood Vessels Sprout Under Pressure Feb. 29, 2016 It is blood pressure that drives the opening of small capillaries during angiogenesis. A team of researchers has observed the process for the first ... read more Feb. 29, 2016 A team of researchers has identified a new mechanism that regulates the effect of the satiety hormone leptin. The study identified the enzyme HDAC5 as key factor in our control of body weight and ... read more Making Better Enzymes and Protein Drugs Feb. 29, 2016 Natural selection results in protein sequences that are only soluble to the level that is required to carry out its physiological function. However, in biotechnological applications, we need these ... read more Feb. 29, 2016 The development of every animal in the history of the world began with a simple step: the fusion of a spermatozoon with an oocyte. Despite the ubiquity of this process, the actual mechanisms through ... read more Feb. 29, 2016 When venom from animals such as spiders, snakes or cone snails is injected via a bite or harpoon, the cocktail of toxins delivered to its victim tends to cause serious reactions that, if untreated, ... read more

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Laser Genetics – Night Vision, Green Lasers for Law …

Thursday, August 4th, 2016

With low energy use and high illumination yield, the ND Series of Laser Designators enables you to focus full illumination where you need it most, with the least loss of light due to flooding. The ND Series puts you in full control of directed laser light for maximum illumination of the intended object.

Laser Genetics utilizes exclusive patented optical laser technology to develop the lighting instruments of tomorrow for civilian and professional use. With its headquarters in Fort Lauderdale, Florida Laser Genetics of America is now one of the nations fastest growing manufacturers of personal-use laser lighting products.

LGA is dedicated to developing high efficiency laser illumination products specific for outdoors, law enforcement, military, marine, EMT, and home defense use.

Through extensive research, LGA has developed a product line that is more than just a laser pointer. The ND-3 Series, ND-3 Subzero series and the ND-5 Laser Illuminator are hand held laser products that utilize new laser technology that delivers the ultimate night vision solution at an affordable price and suitable for any weather condition.

Common for all Laser Genetics products is the patented optical collimator. Through a quick and easy to use, one hand adjustment of the beam diameter, you will be able to focus illumination where you need it most. By adjusting the beam to a wide diameter, you can light up any object in low or no light conditions, or pinpoint a target in close quarters with minimal natural light. Contrary, by adjusting the beam to a narrow and more intense light it could be used to illuminate your target up to 500 yards* or used as a bright signaling device for search and rescue in case of an emergency situation.

The ND-3 Series Laser Designators and the ND-5 Laser Illuminator are developed to be used in weather conditions of 40 F. or above. For cold weather situations in temperatures of 40 F. and below, we recommend using the NEWLY designed Subzero line of products. Through innovative technology and unique circuitry they are specifically designed to operate without loss of power in subzero temperatures.

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An Introduction to Genetics and Genetic Testing – KidsHealth

Thursday, August 4th, 2016

Genetic tests are done by analyzing small samples of blood or body tissues. They determine whether you, your partner, or your baby carry genes for certain inherited disorders.

Genetic testing has developed enough so that doctors can often pinpoint missing or defective genes. The type of genetic test needed to make a specific diagnosis depends on the particular illness that a doctor suspects.

Many different types of body fluids and tissues can be used in genetic testing. For deoxyribonucleic acid (DNA) screening, only a very tiny bit of blood, skin, bone, or other tissue is needed.

For genetic testing before birth, pregnant women may decide toundergo amniocentesis or chorionic villus sampling. There is also a blood test available to women to screen for some disorders. If this screening test finds a possible problem, amniocentesis or chorionic villus sampling may be recommended.

Amniocentesis is a test usually performed between weeks 15 and 20of a woman's pregnancy. The doctor inserts a hollow needle into the woman's abdomen to remove a small amount of amniotic fluid from around the developing fetus. This fluid can be tested to check for genetic problems and to determine the sex of the child. When there's risk of premature birth, amniocentesis may be done to see how far the baby's lungs have matured. Amniocentesis carries a slight risk of inducing a miscarriage.

Chorionic villus sampling (CVS) is usually performed between the 10th and 12th weeks of pregnancy. The doctor removes a small piece of the placenta to check for genetic problems in the fetus. Because chorionic villus sampling is an invasive test, there's a small risk that it can induce a miscarriage.

A doctor may recommend genetic counseling or testing for any of the following reasons:

Although advances in genetic testing have improved doctors' ability to diagnose and treat certain illnesses, there are still some limits. Genetic tests can identify a particular problem gene, but can't always predict how severely that gene will affect the person who carries it. In cystic fibrosis, for example, finding a problem gene on chromosome number 7 can't necessarily predict whether a child will have serious lung problems or milder respiratory symptoms.

Also, simply having problem genes is only half the story because many illnesses develop from a mix of high-risk genes and environmental factors. Knowing that you carry high-risk genes may actually be an advantage if it gives you the chance to modify your lifestyle to avoid becoming sick.

As research continues, genes are being identified that put people at risk for illnesses like cancer, heart disease, psychiatric disorders, and many other medical problems. The hope is that someday it will be possible to develop specific types of gene therapy to totally prevent some diseases and illnesses.

Gene therapy is already being studied as a possible way to treat conditions like cystic fibrosis, cancer, and ADA deficiency (an immune deficiency), sickle cell disease, hemophilia, and thalassemia. However, severe complications have occurred in some patients receiving gene therapy, so current research with gene therapy is very carefully controlled.

Although genetic treatments for some conditions may be a long way off, there is still great hope that many more genetic cures will be found. The Human Genome Project, which was completed in 2003, identified and mapped out all of the genes (about 25,000) carried in our human chromosomes. The map is just the start, but it's a very hopeful beginning.

Date reviewed: April 2014

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An Introduction to Genetics and Genetic Testing - KidsHealth

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Human Genetics – Population Genetics

Thursday, August 4th, 2016

for 1st YEAR STUDENTS INTRODUCTION

he applications of Mendelian genetics, chromosomal abnormalities, and multifactorial inheritance to medical practice are quite evident. Physicians work mostly with patients and families. However, as important as they may be, genes affect populations, and in the long run their effects in populations have a far more important impact on medicine than the relatively few families each physician may serve. It is important that certain polymorphisms are maintained so that the species may survive, even at the expense of individuals. Genetic polymorphisms often are detrimental to the homozygote, but they allow others of the species to survive. Before medical intervention was possible, populations that lacked the sickle cell anemia allele could not survive in the malaria regions of West Africa. Those that had the sickle cell anemia allele survived, and the gene remains in the population at high frequency today, even though the homozygous recessive phenotype was at a severe disadvantage in the past. The high rate of thalassemia in people of Mediterranean origin, the high rate of sickle cell anemia in people of West African descent, the high rate of cystic fibrosis in people from Western Europe, and the high rate of Tay-Sachs disease in ethnic groups from Eastern Europe may all owe their origin to environmental factors that cause changes in gene frequencies in large populations by giving some advantage to heterozygotes who carry a deleterious allele. Although one may never use the calculations of population genetics in medical practice, the underlying principles should be understood.

Population genetics is also the most widely misused area of human genetics, sometimes bordering on "vigilante genetics," a term coined by Newton Morton. Persons have mistakenly applied population genetics to "prove" race superiority for intelligence and aptitudes, and have misused it in eugenics. As an educated and, I hope, a respected member of your community you must be alert to "vigilante genetics."

Population genetics is concerned with gene and genotype frequencies, the factors that tend to keep them constant, and the factors that tend to change them in populations. It is largely concerned with the study of polymorphisms. It directly impacts counseling, forensic medicine, and genetic screening.

Consider a population of 1000 individuals all typed for the simplest test at the MN blood group locus. At its most simplistic form this locus can be reduced to a codominant system with two alleles M and N. (In reality it is considerably more complex than this but this simple form will suffice for our examples.) Every individual in the population will be either M (having two M alleles), MN (heterozygous), or N (having two N alleles). Suppose the blood typing results were as follows: 300 M individuals, 600MN individuals, and 100 N individuals. You probably want to ask, "What is the gene frequency of the M allele in the above population of 1000 individuals?" I'm glad you're interested!

1000 individuals each have two alleles at the MN locus = 2000 genes

Each M individual has 2 M alleles 300 x 2 = 600 M alleles

Each MN individual has 1 M allele 600 x 1 = 600 M alleles

There is a total of 1200 M genes in a population of 2000 genes. The gene frequency of the M allele is 1200/2000 = 0.6

I'll bet you want to know, "What is the gene frequency of the N allele?" Well, I'll show you how to find out.

Each MN individual has 1 N allele 600 x 1 = 600 N genes

Each N individual has 2 N genes 100 x 2 = 200 N genes

Again, there is a total of 2000 genes in the population for the MN locus. The gene frequency of the N allele is 800/2000 = 0.4

Notice that when there are only two alleles in the population, their gene frequencies must add to 1. If they don't, you've done something wrong. This counting method of calculating the gene frequency must be used whenever the heterozygote can be detected.

Gene frequency = (2 x homozygote + heterozygote) / 2 x population

Gene frequency for one allele = 1 - gene frequency of the other allele

These two general formulas assume nothing of the population, only that it is a single interbreeding group. All other methods make some assumptions of the population in order to simplify calculations.

For many human autosomal recessive traits the heterozygote cannot be distinguished from the normal homozygote. When this occurs the Hardy-Weinberg equilibrium is assumed to apply. These authors, Hardy in England and Weinberg in Germany, used different approaches but came to the same conclusions in 1908. They made several assumptions of the population:

Under these assumptions, Hardy and Weinberg found that the gene frequency and the genotype frequency in the population do not change from generation to generation. Furthermore, if the frequency of the dominant allele A in the founding population was p , and the frequency of the recessive allele a in the founding population was q, then after one generation of random mating the genotype frequencies would remain fixed and would be in the ratio:

If you want to see evidence that this is true, see Figure 20. If, on the other hand, you believe everything you read, and only want to study what will be covered on the examination, continue on.

Hopefully, someone will ask the question, "Is there any evidence that the human population meets the requirements of Hardy-Weinberg equilibrium, or is this just a mental exercise?" Of course there is evidence! Consider the following:

In my experience, one may use several criteria for selecting a person to mate with, but one usually doesn't select a mate based on blood types at the MN blood group locus. Therefore, we might assume that this locus would be a good test of random mating. All of the other Hardy-Weinberg criteria also seem to be met. Mutations at this autosomal locus are rare. We know of no selective advantage or disadvantage in the present environment. And migration wouldn't be much of a factor if we took the sample at one short interval of time. This locus should provide a good test.

We have already seen that gene frequencies and genotype frequencies for this locus can be determined without using assumptions of Hardy-Weinberg equilibrium. Let's see if a real population sample is distributed as p2 (M), 2pq (MN), q2 (N).

In 1975, Race and Sanger reported the typing results from 1279 individuals in London. They were not collecting these data for the purpose of testing for Hardy-Weinberg equilibrium, so they could not be accused of typing individuals until a certain distribution was achieved, a question that has always remained about Mendel's original studies. Race and Sanger found 363 persons were M, 634 were MN, and 282 were N. Using our original method of calculating gene frequencies, the frequency of the M allele (p) would be:

p = (2 x 363) + 634 / (2 x 1279) = 0.53167

The frequency of the N allele (q) would be:

q = (2 x 282) + 634 / (2 x 1279) = 0.46833

If the population were in Hardy-Weinberg equilibrium, then the number of M individuals should be p2 x 1279, the number of MN individuals should be 2pq x 1279, and the number of N individuals should be q2 x 1279, or

For the MN blood group locus there can be little doubt that the conditions for Hardy-Weinberg equilibrium are met in the human population, at least the population in London where the sample was taken. The observed frequencies closely approximate what would be expected if the population were in Hardy-Weinberg equilibrium.

This gives us the assurance that we can use Hardy-Weinberg as a method when the heterozygote cannot be detected. An example of the use of the Hardy-Weinberg principle in medical genetics is given below.

Suppose there is an autosomal recessive disease where the frequency of affected in the population is 1/10,000. If the population is in Hardy-Weinberg equilibrium, this frequency would equal q2. The gene frequency of the recessive allele (q) would then be the square root of q2, or the square root of 1/10,000 which equals 1/100. The carrier (heterozygote) frequency (2pq) is usually approximated as 2q since p (0.99) is so close to 1. The carrier frequency is then 1/50.

For an autosomal recessive disease with a population frequency of 1/10,000, the carrier frequency is 1/50. Put another way, on average, as many as 3 or 4 first year medical students at UIC are carriers of such a disease.

From time to time, certain groups have suggested that the way to eliminate a deleterious disease from the population is to not allow affected individuals to mate. The above example should provide some evidence that this will have little effect on gene frequencies in the population. Although the frequency of the disease is only 1/10,000, (we should have one affected first year medical student at UIC every 50 years) the carrier frequency is 1/50 (we should have 3 or 4 carriers at UIC in every incoming class). These phenotypically normal carriers will keep the gene in the population.

If, by chance, a student in the first year class has a sibling with an autosomal recessive disease that is present at birth, the student would have a 2/3 chance of being a carrier. If that student were to have a child with an unrelated partner selected at random from the general population, and the disease frequency in the general population is 1/10,000, the probability of their child being affected is:

Compare that to the probability that two unrelated individuals, with no history of the disease in their families would have an affected child, when the carrier frequency is 1/50:

Since it is a stated goal of medicine to do what is best for the patient, what happens to genes in populations when exceptions to Hardy-Weinberg occur?

Although mutation rates are usually very low, geneticists have long been concerned about environmental factors that will lead to even slight increases. There are two general types of mutation, a mutation that changes a gene that makes a functional product into a gene that makes a nonfunctional product (forward mutation) and a mutation that changes a gene that makes a nonfunctional product into a gene that makes a functional product (reverse mutation). Several events can lead to a forward mutation, base change, base insertion, base deletion, etc., but a reverse mutation must correct the specific change that produced the original forward mutation. For example if a single base deletion caused the original forward mutation, then that base must be re-inserted in exactly the same place for a reverse mutation to occur. In general, forward mutations occur at a frequency that is at least 10 times that of reverse mutations. A method of estimating forward mutation rates is given in Gelehrter, Collins, and Ginsburg, 2nd ed., Chapter 4. Students will be well advised to read this chapter carefully.

If is the forward mutation rate from a functional to a nonfunctional allele, and is v the reverse mutation rate from a nonfunctional allele to a functional allele at the same locus, an equilibrium will be established between these two mutation rates that determines q, the gene frequency of the nonfunctional allele.

At equilibrium, q = /(+v)

If v is truly one tenth the frequency of , then we can assign the value 1 for v and 10 as the value for . The above equation reduces to

qequil = 10/(10+1) or 10/11 =0.90909090909

Gene frequencies for nonfunctional alleles tend to increase in the population because of recurrent mutation. They will not entirely eliminate functional alleles but they tend to replace them, and can, if no other factors are involved, reach very high frequencies.

As a possible human example of the effects of recurrent mutation consider the following. In the ABO blood group system, there are two functional alleles, A and B. Alleles A and B control transferase enzymes that connect the proper sugar molecule (glucosamine or n-acetyl glucosamine) to a common precursor substance. Most likely, B was the result of arare mutation of the A allele. O is a nonfunctional allele that recognizes no substrate, and no sugar molecule is transferred, leaving the precursor unchanged. In the ABO system, O is now the most frequent allele. If there is no selective advantage, O should continue to increase at the expense of A and B.

The derivations of the equations used to calculate the effects of recurrent mutation are shown in Figure 21. Again, if you are interested only in studying for possible test questions, this material is not required.

Assume a population of N individuals with two alleles at a locus, D with a frequency of p and d with a frequency of q. At generation 0 there will be 2Np D alleles , or 2N(1-q) D alleles, and 2Nq d alleles. Assume D mutates to d at a frequency of and that d mutates to D at a frequency of v. Assume that is 10 times as frequent as v. Then at generation 1 the number of d alleles (2Nq1) would be:

2Nq1 = 2Nq (from gen. 0) + 2N (1-q) (mutations from D to d) - 2Nqv (mutations from d to D)

This reduces to:

q1 = q + (1-q) - qv Or the change in q = q1 - q or the change in q = q + (1-q) - qv - q

At equilibrium the change in q = 0, so at equilibrium 0 = q +(1-q) -qv -q, or, qv = (1-q), or, qv = - q

This reduces to q (at equilibrium) = /(+v)

One factor assumed in the discussion of recurrent mutation was that the nonfunctional allele and the functional allele have the same selective advantage. This may be true of the ABO blood group system, but it is not usually true of autosomal recessive diseases. The disease state, by definition, is always a deleterious phenotype. In autosomal recessive diseases the phenotype is almost always the result of nonfunctional alleles in the homozygous state. If left untreated the recessive phenotype for a disease would be less fit than the heterozygote or normal homozygote. How does selection against the homozygous recessive individual affect gene frequencies in the population?

Fitness, to a geneticist, is not the same as fitness to a movie director or a sports columnist. Fitness is not measured by physical attributes, it is measured by the number of offspring produced in the next generation that survive and reproduce. In a hunting-gathering society, the most fit person may have been the near sighted male who could not go on the hunt because he would stumble and make too much noise. If he were left behind to gather fruit and berries with the women, he may have become the most fit person in the tribe. Grandchildren, great-grandchildren, etc., are the best measures of the fitness of an individual. This has alway been my favorite explanation of why so many of us are near sighted, and why society changed from hunting-gathering to agriculture. It's all population genetics!

The most fit phenotype in the population is assigned a fitness of 1. If there are two equally fit phenotypes, each is assigned a fitness of 1. Those less fit must be assigned a fitness of less than 1. The difference between 1 and the fitness value is called the selection coefficient. The relationship between fitness, w, and the selection coefficient, s, is given by the equation, w = 1-s. The textbook uses f as the symbol for fitness, although historically most geneticists reserve f as the symbol for the inbreeding coefficient and use w as the symbol for fitness.

The effect of selection against the recessive phenotype is that, no matter how little the selection coefficient, as long as s is not 0, recessive alleles will be lost at each generation until no more remain in the population. Selection tends to reduce nonfunctional recessive alleles from the population; recurrent mutation tends to create nonfunctional recessive alleles in the population. The derivations of the effects of selection against the recessive phenotype are shown if Figure 22. Again, the material in Figure 22 will not be examined in this course.

The frequency of q in generation 1, q1, = (2 x homozygote + heterozygote)/ 2 x total

q1 = [2(1-s)q2 + 2pq]/ 2(1-sq2) , and q, the change in q, = q1 - q

q = [(1-s)q2 + (1-q)q]/ (1-sq2) , which reduces to q = [-spq2]/ (1-sq2)

q = 0 only when q = 0. There will be no equilibrium until the recessive allele is eliminated.

Since mutation tends to increase nonfunctional alleles in the population, and selection against the recessive phenotype tends to remove them, is there a point where these two will reach an equilibrium where gene frequencies remain stable from generation to generation? Again, if is the mutation rate, and s is the selection coefficient, an equilibrium will be reached when

= sq2

If the fitness of the homozygous recessive individual is 0, that is, the individual with that phenotype cannot reproduce, then s equals 1 and the above equation reduces to

= q2

The disease frequency cannot go lower than the recurrent mutation rate, even if affected individuals cannot reproduce.

The derivations of these equations are shown in Figure 23.

For mutation, the change in q = - q -qv. For selection, the change in q = [-spq2]/ [1-sq2]. If they balance at an equilibrium, the net effect is that they should sum to 0.

- q - qv + ([-spq2]/[1-sq2]) = 0

To simplify calculations, we will get rid of second order variables (qv) is only 1/10 of (q) and can be eliminated. Similarly, sq2 is very small in the denominator when compared to 1, and can be eliminated. This reduces the equation to

-q - spq2 = 0 to first order magnitude.

This reduces to - q = s(1-q) q2 or (1 - q) = (1-q)sq2

At equilibrium, = sq2 to first order magnitude.

Some genes exist at a rather high frequency in the population because the heterozygote is more fit than either homozygote. The only documented example of this is sickle cell anemia in Western Africa. There are three major genotypes for the sickle cell locus, each producing a different phenotype, in West Africans, AA, or normal individuals, AS or heterozygote individuals (often called carriers), and SS individuals who will have sickle cell anemia. Without medical intervention, SS individuals will have a fitness less than 1. In the falciparum malarial environment of West Africa, AA and AS individuals get malaria, but AS individuals usually have much milder cases of the disease and usually survive while AA individuals are less likely to do so. The heterozygote is the most fit phenotype of the three. If the selection coefficient against the homozygous normal AA individual is t, and the selection coefficient against the homozygous SS individual is s, and if p is the frequency of the A allele and q the frequency of the S allele then an equilibrium will be reached in which

p = s/(s + t) and q = t/(s + t). The gene frequencies at equilibrium are determined only by the relative sizes of the selection coefficients, not by their absolute magnitudes.

The derivations of these formulas are shown in Figure 24. Again, you are not responsible for knowing how to derive these formulas.

The gene frequency of the q allele at generation 1, q1 = [2pq + 2q2(1-s)]/2[1- tp2 - sq2]

Again the change in q, q, = q1 - q and at equilibrium, q = 0

0 = [pq + (1-s)q2/ [1-tp2-sq2] Substituting (1- q) for p, this equation will reduce to:

0 = -spq + tp2 or sq = tp

When (1-q) is substituted for p or (1-p) is substituted for q, this reduces to:

q = t/(s + t) and p = q/(s + t).

Assortive mating in humans may occur to a limited degree for traits such as intelligence. In some studies, married couples have higher correlation coefficients for intelligence than do siblings. In modern western culture, we tend to marry someone who is about our own intelligence, although this is probably an over simplification. If intelligence were controlled by a single genetic locus with two alleles, S for smart and D for dumb, then three phenotypes would be possible, SS for smart persons, SD for persons with average intelligence, and DD for persons who are mentally challenged. Of course, we know that intelligence is a multifactorial trait and not a single gene trait, but it is interesting to see what happens if it were a single gene trait with assortive mating where smart persons were only allowed to mate with smart persons, average persons with average persons, and mentally challenged only with mentally challenged. Strangely enough the gene frequencies do not change, only the genotype frequencies. The results are shown in Figure 25.

Two different populations result, one smart, the other mentally challenged. Average gets lost. Assortive mating eventually results in two species being formed from one.

Gene frequencies in small isolate populations do not reflect those of the larger founding population from which they were derived because of two factors, founder effect and random genetic drift. Founder effect occurs when the population grew from a few founding individuals. A few individuals cannot represent all of the genomes of the founding population. As we discussed before, each of us is carrying from 1 to 8 mutant genes in the heterozygous state, even though we are normal. When the founding population is small, intermarriage must result even though steps are taken to avoid it. The mutations carried by the founders are in higher frequency than they would be in the general population from which the founders came. Island populations founded by pirates or shipwreck, that were isolated for several generations tend to have different gene and genotype frequencies because of founder effect. Similarly, religious isolates, where marriage outside the religion is forbidden, also have founder effects.

Even if the founders of small isolate populations had exactly the same genotypes and gene frequencies of the original parent population, gene and genotype frequencies would change because of random genetic drift. Random genetic drift occurs because a small population cannot maintain randomness. Consider a population with 10 individuals with only two alleles at a locus, D with a frequency of 0.5 and d with a frequency of 0.5. By chance alone one would expect to find 10D and 10 d gametes being passed to the next generation. But one may find 11 D and only 9 d gametes. The next generation, one could find 10 and 10 again, or could find 12 and 8. But suppose after drifting to 12 D and 8 d, by chance a really skewed sampling occurred and one got 15 D and 5 d. It would be difficult, if not impossible to get back to the original 10D and 10 d. Sampling errors in small populations are always going to occur if given enough opportunities. These errors assure that random genetic drift will always occur. Isolate populations never have the same gene and genotype frequencies as their founding populations.

It is obvious that the major difference between autosomal loci and X-linked loci in populations is that the males (usually half the population) have only one X. Males cannot have the distribution, p2, 2pq, and q2 because they have only one X, they have either the normal allele p, or the recessive allele, q. In males, gene and genotype frequencies are the same. Thus, the genotype frequencies in the male and female can never be the same. In addition, there can be no heterozygote x heterozygote mating class since there are no male heterozygotes, and as of this date females cannot mate and produce a child. X-linked traits can reach stable gene frequencies in males and females, but cannot reach Hardy-Weinberg equilibrium.

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Human Genetics - Population Genetics

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Genetics | Carolina.com

Thursday, August 4th, 2016

Introducing our NEW "Cracking The Code On Genetics" Series

Explore key topics & how to incorporate them into lessons Download 40+ FREE teaching tools & activities Enter to win $2000 in Genetics Product Bundles

My Carolina Connections is the new on-demand webinar series designed for the busy science educator. Experience our first on-demand webinar, Using Model Organisms, and follow our interactive Q & A session on Twitter #carolinagenetics.

Can creating mutations be good? The answer is yes. In fact, RNA Interference (turning off genes) is a genetic breakthrough that's already being used to develop new treatments for cancer and other diseases.

Carolina offers a variety of resources and products to help your students delve into this emerging area. For example, students can induce RNAi (and witness the results) simply by feeding roundworms bacteria that turn off certain genes.

There's nothing like real, live organisms to drive home genetic concepts. And there's no other company that can match Carolina's model organisms selectionfrom corn to fruit flies to our exclusive Wisconsin Fast Plants.

Check out this infographic to learn more about the benefits, life cycle, available phenotypes and other information on 3 model organisms.

Ready to breathe new life into your genetics lessons?

Do your students struggle with Mitosis and Meiosis? Many do. We find it works best to approach this topic from different anglesgiving students the opportunity for hands-on cell cycle exploration.

Our NEW Mitosis Matchup activity is an easy, visual way to demonstrate orientation, organization and other cell phase characteristics.

Whether you're laying the foundation with Mitosis or exploring Mendels Laws in Meiosis, Carolina has the products and resources you need.

A solid foundation in DNA is essential before exploring more advanced genetic concepts.

Fortunately, we have a 3D animated video that shows your students exactly how DNA is packaged. It demonstrates how 6 feet of DNA can be packed into the microscopic nucleus of every cell.

Bring this video and Carolina's great new products and activities into your classroom and students will be differentiating chromosomes, genes and alleles in no time!

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Department of Genetics at Washington University St. Louis

Thursday, August 4th, 2016

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Department of Genetics at Washington University St. Louis

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Genetics – Genetic inheritance – NHS Choices

Thursday, August 4th, 2016

Each cell in the body contains 23 pairs of chromosomes. One chromosome from each pair is inherited from your mother and one is inherited from your father.

The chromosomes contain the genes you inherit from your parents. There may be different forms of the same gene called alleles.

For example, for the gene that determines eye colour, you may inherit a brown allele from your mother and a blue allele from your father. In this instance, you will end up with brown eyes because brown is the dominant allele. The different forms of genes are caused by mutations (changes) in the DNA code.

The same is true for medical conditions. There may be a faulty version of a gene that results in a medical condition, and a normal version that may not cause health problems.

Whether your child ends up with a medical condition will depend on several factors, including:

Genetic mutations occur when DNA changes, altering the genetic instructions. This may result in a genetic disorder or a change in characteristics.

Mutations can be caused by exposure to specific chemicals or radiation. For example, cigarette smoke is full of chemicals that attack and damage DNA. This causes mutations in lung cell genes, including the ones that control growth. In time, this can lead to lung cancer.

Mutations can also occur when DNA fails to be copied accurately when a cell divides.

Mutations can have three different effects. They may:

Some medical conditions are directly caused by a mutation in a single gene that may have been passed onto a child by his or her parents. These are known as monogenic conditions.

Depending on the specific condition concerned, monogenic conditions can be inherited in three main ways. These are outlined below.

For conditions that are inherited in an autosomal recessive pattern to be passed on to a child, both parents must have a copy of the faulty gene (they are carriers of the condition).

If the child only inherits one copy of the faulty gene, they will be a carrier of the condition but will not have the condition themselves.

If a mother and a father both carry the faulty gene, there is a one in four (25%) chance of each child they have inheriting the genetic condition and a one in two chance (50%) of them being a carrier.

Examples of genetic conditions inherited in this way include:

For conditions that are inherited in an autosomal dominant pattern to be passed on to a child, only one parent needs to carry the mutation.

If one parent has the mutation, there is a one in two (50%) chance it will be passed on to each child the couple has.

Examples of genetic conditions inherited in this way include:

Some conditions are caused by a mutation on the X chromosome (one of the sex chromosomes). These are usually inherited in a recessive pattern albeit in a slightly different way to the autosomal recessive pattern described above.

X-linked recessive conditions often don't affect females to a significant degree because females have two X chromosomes, one of which will almost certainly be normal and can usually compensate for the mutated chromosome. However, females who inherit the mutation will become carriers.

If a male inherits the mutation from his mother (males cannot inherit X-linked mutations from their fathers because they will receive a Y chromosome from them), he will not have a normal copy of the gene and will develop the condition.

Whena mother is a carrier of an X-linked mutation, each daughter they have has a one in two (50%) chance of becoming a carrier and each son they have has a one in two (50%) chance of inheriting the condition.

When a father has an X-linked condition, his sons will not be affected because he will pass on a Y chromosome to them. However, any daughters he has will become carriers of the mutation.

Examples of genetic conditions inherited in this way include:

Although genetic conditions are often inherited, this is not always the case. Some genetic mutations can occur for the first time when a sperm or egg is made, when a sperm fertilises an egg, or when cells are dividing after fertilisation. This is known as a 'de novo' or 'sporadic' mutation.

Someone with a new mutation will not have a family history of a condition, but they may be at risk of passing the mutation on to their children. They may also have, or be at risk of developing, a form of the condition themselves.

Examples of conditions that are often caused by a de novo mutation include some types of muscular dystrophy, haemophilia and type 1 neurofibromatosis.

Some conditions are not caused by a mutation on a specific gene, but by an abnormality in a person's chromosomes such as having too many or too few chromosomes, rather than the normal 23 pairs.

Examples of conditions caused by chromosomal abnormalities include:

While these are genetic conditions, they are generally not inherited. Instead, they usually occur randomly as a result of a problem before, during, or soon after the fertilisation of an egg by a sperm.

Very few health conditions are only caused by genes most are caused by the combination of genes and environmental factors. Environmental factors include lifestyle factors, such as diet and exercise.

Around a dozen or so genes determine most human characteristics, such as height and the likelihood of developing common conditions.

Genes can have many variants, and studies of the whole genome (the whole set of genes) in large numbers of individuals are showing that these variants may increase or decrease a persons chance of having certain conditions. Each variant may only increase or decrease the chance of a condition very slightly, but this can add up across several genes.

In most people, the gene variants balance out to give an average risk for most conditions but, in some cases, the risk is significantly above or below the average. It is thought that it may be possible to reduce the risk by changing environmental and lifestyle factors.

For example, coronary heart disease (when the heart's blood supply is blocked or interrupted) can run in families, but a poor diet, smoking and a lack of exercise can also increase your risk of developing the condition.

Research suggests that in the future it will be possible for individuals to find out what conditions they are most likely to develop. It may then be possible for you to significantly reduce the chances of developing these conditions by making appropriate lifestyle and environmental changes.

The two strands of DNA are wound around each other into a double helix

Page last reviewed: 07/08/2014

Next review due: 07/08/2016

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heredity | genetics | Britannica.com

Thursday, August 4th, 2016

Heredity,chromosome Howard Sochurek/Corbisthe sum of all biological processes by which particular characteristics are transmitted from parents to their offspring. The concept of heredity encompasses two seemingly paradoxical observations about organisms: the constancy of a species from generation to generation and the variation among individuals within a species. Constancy and variation are actually two sides of the same coin, as becomes clear in the study of genetics. Both aspects of heredity can be explained by genes, the functional units of heritable material that are found within all living cells. Every member of a species has a set of genes specific to that species. It is this set of genes that provides the constancy of the species. Among individuals within a species, however, variations can occur in the form each gene takes, providing the genetic basis for the fact that no two individuals (except identical twins) have exactly the same traits.

heredityEncyclopdia Britannica, Inc.The set of genes that an offspring inherits from both parents, a combination of the genetic material of each, is called the organisms genotype. The genotype is contrasted to the phenotype, which is the organisms outward appearance and the developmental outcome of its genes. The phenotype includes an organisms bodily structures, physiological processes, and behaviours. Although the genotype determines the broad limits of the features an organism can develop, the features that actually develop, i.e., the phenotype, depend on complex interactions between genes and their environment. The genotype remains constant throughout an organisms lifetime; however, because the organisms internal and external environments change continuously, so does its phenotype. In conducting genetic studies, it is crucial to discover the degree to which the observable trait is attributable to the pattern of genes in the cells and to what extent it arises from environmental influence.

Because genes are integral to the explanation of hereditary observations, genetics also can be defined as the study of genes. Discoveries into the nature of genes have shown that genes are important determinants of all aspects of an organisms makeup. For this reason, most areas of biological research now have a genetic component, and the study of genetics has a position of central importance in biology. Genetic research also has demonstrated that virtually all organisms on this planet have similar genetic systems, with genes that are built on the same chemical principle and that function according to similar mechanisms. Although species differ in the sets of genes they contain, many similar genes are found across a wide range of species. For example, a large proportion of genes in bakers yeast are also present in humans. This similarity in genetic makeup between organisms that have such disparate phenotypes can be explained by the evolutionary relatedness of virtually all life-forms on Earth. This genetic unity has radically reshaped the understanding of the relationship between humans and all other organisms. Genetics also has had a profound impact on human affairs. Throughout history humans have created or improved many different medicines, foods, and textiles by subjecting plants, animals, and microbes to the ancient techniques of selective breeding and to the modern methods of recombinant DNA technology. In recent years medical researchers have begun to discover the role that genes play in disease. The significance of genetics only promises to become greater as the structure and function of more and more human genes are characterized.

This article begins by describing the classic Mendelian patterns of inheritance and also the physical basis of those patternsi.e., the organization of genes into chromosomes. The functioning of genes at the molecular level is described, particularly the transcription of the basic genetic material, DNA, into RNA and the translation of RNA into amino acids, the primary components of proteins. Finally, the role of heredity in the evolution of species is discussed.

Heredity was for a long time one of the most puzzling and mysterious phenomena of nature. This was so because the sex cells, which form the bridge across which heredity must pass between the generations, are usually invisible to the naked eye. Only after the invention of the microscope early in the 17th century and the subsequent discovery of the sex cells could the essentials of heredity be grasped. Before that time, ancient Greek philosopher and scientist Aristotle (4th century bc) speculated that the relative contributions of the female and the male parents were very unequal; the female was thought to supply what he called the matter and the male the motion. The Institutes of Manu, composed in India between 100 and 300 ad, consider the role of the female like that of the field and of the male like that of the seed; new bodies are formed by the united operation of the seed and the field. In reality both parents transmit the heredity pattern equally, and, on average, children resemble their mothers as much as they do their fathers. Nevertheless, the female and male sex cells may be very different in size and structure; the mass of an egg cell is sometimes millions of times greater than that of a spermatozoon.

heredityHulton Archive/Getty ImagesThe ancient Babylonians knew that pollen from a male date palm tree must be applied to the pistils of a female tree to produce fruit. German botanist Rudolph Jacob Camerarius showed in 1694 that the same is true in corn (maize). Swedish botanist and explorer Carolus Linnaeus in 1760 and German botanist Josef Gottlieb Klreuter, in a series of works published from 1761 to 1798, described crosses of varieties and species of plants. They found that these hybrids were, on the whole, intermediate between the parents, although in some characteristics they might be closer to one parent and in others closer to the other parent. Klreuter compared the offspring of reciprocal crossesi.e., of crosses of variety A functioning as a female to variety B as a male and the reverse, variety B as a female to A as a male. The hybrid progenies of these reciprocal crosses were usually alike, indicating that, contrary to the belief of Aristotle, the hereditary endowment of the progeny was derived equally from the female and the male parents. Many more experiments on plant hybrids were made in the 1800s. These investigations also revealed that hybrids were usually intermediate between the parents. They incidentally recorded most of the facts that later led Gregor Mendel (see below) to formulate his celebrated rules and to found the theory of the gene. Apparently, none of Mendels predecessors saw the significance of the data that were being accumulated. The general intermediacy of hybrids seemed to agree best with the belief that heredity was transmitted from parents to offspring by blood, and this belief was accepted by most 19th-century biologists, including English naturalist Charles Darwin.

The blood theory of heredity, if this notion can be dignified with such a name, is really a part of the folklore antedating scientific biology. It is implicit in such popular phrases as half blood, new blood, and blue blood. It does not mean that heredity is actually transmitted through the red liquid in blood vessels; the essential point is the belief that a parent transmits to each child all its characteristics and that the hereditary endowment of a child is an alloy, a blend of the endowments of its parents, grandparents, and more-remote ancestors. This idea appeals to those who pride themselves on having a noble or remarkable blood line. It strikes a snag, however, when one observes that a child has some characteristics that are not present in either parent but are present in some other relatives or were present in more-remote ancestors. Even more often, one sees that brothers and sisters, though showing a family resemblance in some traits, are clearly different in others. How could the same parents transmit different bloods to each of their children?

Mendel disproved the blood theory. He showed (1) that heredity is transmitted through factors (now called genes) that do not blend but segregate, (2) that parents transmit only one-half of the genes they have to each child, and they transmit different sets of genes to different children, and (3) that, although brothers and sisters receive their heredities from the same parents, they do not receive the same heredities (an exception is identical twins). Mendel thus showed that, even if the eminence of some ancestor were entirely the reflection of his genes, it is quite likely that some of his descendants, especially the more remote ones, would not inherit these good genes at all. In sexually reproducing organisms, humans included, every individual has a unique hereditary endowment.

Lamarck, Jean-Baptiste Photos.com/ThinkstockLamarckisma school of thought named for the 19th-century pioneer French biologist and evolutionist Jean-Baptiste de Monet, chevalier de Lamarckassumed that characters acquired during an individuals life are inherited by his progeny, or, to put it in modern terms, that the modifications wrought by the environment in the phenotype are reflected in similar changes in the genotype. If this were so, the results of physical exercise would make exercise much easier or even dispensable in a persons offspring. Not only Lamarck but also other 19th-century biologists, including Darwin, accepted the inheritance of acquired traits. It was questioned by German biologist August Weismann, whose famous experiments in the late 1890s on the amputation of tails in generations of mice showed that such modification resulted neither in disappearance nor even in shortening of the tails of the descendants. Weismann concluded that the hereditary endowment of the organism, which he called the germ plasm, is wholly separate and is protected against the influences emanating from the rest of the body, called the somatoplasm, or soma. The germ plasmsomatoplasm are related to the genotypephenotype concepts, but they are not identical and should not be confused with them.

The noninheritance of acquired traits does not mean that the genes cannot be changed by environmental influences; X-rays and other mutagens certainly do change them, and the genotype of a population can be altered by selection. It simply means that what is acquired by parents in their physique and intellect is not inherited by their children. Related to these misconceptions are the beliefs in prepotencyi.e., that some individuals impress their heredities on their progenies more effectively than othersand in prenatal influences or maternal impressionsi.e., that the events experienced by a pregnant female are reflected in the constitution of the child to be born. How ancient these beliefs are is suggested in the Book of Genesis, in which Laban produced spotted or striped progeny in sheep by showing the pregnant ewes striped hazel rods. Another such belief is telegony, which goes back to Aristotle; it alleged that the heredity of an individual is influenced not only by his father but also by males with whom the female may have mated and who have caused previous pregnancies. Even Darwin, as late as 1868, seriously discussed an alleged case of telegony: that of a mare mated to a zebra and subsequently to an Arabian stallion, by whom the mare produced a foal with faint stripes on his legs. The simple explanation for this result is that such stripes occur naturally in some breeds of horses.

All these beliefs, from inheritance of acquired traits to telegony, must now be classed as superstitions. They do not stand up under experimental investigation and are incompatible with what is known about the mechanisms of heredity and about the remarkable and predictable properties of genetic materials. Nevertheless, some people still cling to these beliefs. Some animal breeders take telegony seriously and do not regard as purebred the individuals whose parents are admittedly pure but whose mothers had mated with males of other breeds. Soviet biologist and agronomist Trofim Denisovich Lysenko was able for close to a quarter of a century, roughly between 1938 and 1963, to make his special brand of Lamarckism the official creed in the Soviet Union and to suppress most of the teaching and research in orthodox genetics. He and his partisans published hundreds of articles and books allegedly proving their contentions, which effectively deny the achievements of biology for at least the preceding century. The Lysenkoists were officially discredited in 1964.

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Genetics, Breeding, & Animal Health : Home

Thursday, August 4th, 2016

The mission of the Genetics, Breeding, and Animal Health Research Unit is to define the role of genetics in animal, pathogen, and microbial community interactions in domestic livestock production. Our overall goal is to develop effective genetic strategies to improve meat quality, animal health, and production efficiency. RESEARCH PROGRAM

Research at USMARC characterizes genetic differences ranging from DNA sequence differences through breed differences. These genetic differences arise by chance in the DNA sequence, by geographic isolation, by the mating restrictions of breed associations, by crossbreeding, and by natural and human imposed selection. Close cooperation with USMARC scientists from many disciplines results in comprehensive evaluations of genetic differences. Collaborations with researchers at other locations across the United States and internationally are used to advance the research.

Genomic scientists skilled in obtaining DNA sequence, identifying sequence differences, developing DNA markers, and determining genotypes have worked with computational biologists trained in comparison and analysis of very large collections of data to achieve significant successes. Until recent efforts to produce whole genome sequences for cattle and pigs, much of the publicly available DNA sequence for these species was developed at USMARC. Many QTL studies with cattle and pigs conducted worldwide use information from the linkage maps developed by USMARC and collaborators. A genetic marker for beef tenderness has been widely adopted by beef genomics companies and beef cattle breeders. A Gene Atlas was developed to identify what genes are being expressed in different tissues. New insights into genome organization, such as microRNA elements and copy number variants, are gained from whole genome sequence and are being evaluated in livestock. It is now feasible to obtain tens and hundreds of thousands of genotypes on a single animal from marker chips. These chips were used to quickly identify a defective mutation for marble bone disease and the affected breed is using a test based on these results to prevent the disease from propagating. Thousands of cattle and pigs at USMARC have been genotyped with these chips and associations with the genetic markers and prediction equations based on the genotypes have been released. The chips are being used to find associations in additional industry animals using a lower-cost method called pooling.

Geneticists skilled in quantitative genetics, experimental design, and statistics develop populations of animals that are measured for traits such as growth, efficiency of production, carcass, meat quality, reproduction, and indicators of health. Information is analyzed to estimate breed differences, heterosis, and heritabilities. Selected populations verify whether predicted selection responses are obtained and correlated changes in other traits are measured. Genomic scientists work with these populations to evaluate linkage and associations of traits with genetic markers. USMARC continues to be a premier source of information on breed differences and heterosis. In cattle, breed differences have been incorporated into across breed EPD adjustments increasing the impact of the research. Current research is expanding to include more direct connections to prominent industry sires. In sheep, emphasis is on easy-care maternal breeds and disease resistance. Selection experiments in pigs and cattle have emphasized selection for reproduction. Results have demonstrated that genetic change can be made even for traits with low heritabilities or genetic antagonisms. Current selection experiments incorporate genetic markers into breeding decisions to evaluate their potential contributions.

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STAR: Genetics – Home

Thursday, August 4th, 2016

StarGenetics is a Mendelian genetics cross simulator developed at MIT by biology faculty, researched-trained scientists and technologists at MIT's OEIT. StarGenetics allows students to simulate mating experiments between organisms that are genetically different across a range of traits to analyze the nature of the traits in question. Its goal is to teach students about genetic experimental design and genetic concepts. For more information on StarGenetics click here.

StarGenetics is freely accessible via the web. Press the Start button to get started.

StarGenetics can be used to teach simple genetics concepts that are appropriate for high school biology students as well as complex genetics concepts that are appropriate for advanced biology undergraduate students.In addition,StarGenetics allows for instructors to customize the exercises presented to the student. To find out how to create your own StarGenetics exerciseand for more information on the concepts that can be taught using StarGenetics, click here.

StarGenetics simulates genetic experiments using known model organisms such as Mendel's garden peas, flies (Drosophila melanogaster), and yeast (Saccharomyces cerevisiae). StarGenetics simulate crosses in cows, which can be use to explore traits in organisms with similar genetics to humans. In addition, StarGenetics can simulate crosses between non-model organisms such as "smiley faces", which are typically used for introducing genetic concepts to younger audiences. The following are the currently available visualizers for StarGenetics:

Examples of genetic experiments in each of the different StarGenetics visualizers (from left to right, clockwise): Fly, Peas, Cow, Smiley Face, Fish, andYeast visualizers. (Click on the image for a larger view)

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Genetics | The Gruber Foundation

Thursday, August 4th, 2016

"Genetics is one of the most far-reaching of the sciences with its potential to alleviate human suffering."

Peter Gruber, Chairman Emeritus and Co-Founder The Gruber Foundation

The Genetics Prize is presented to a leading scientist, or up to three, in recognition of groundbreaking contributions to any realm of genetics research.

The Gruber Foundation established and awarded its first Genetics Prize in 2001. This year of monumental accomplishment in genetics research, with the successful sequencing of the human genome, was a particularly auspicious time to launch the world's first major international prize devoted specifically to achievements in the realm of genetics research.

Created 135 years after Gregor Mendel discovered laws of heredity that implied the existence of genetic factors, the Genetics Prize is awarded under the guidance of an international advisory board of distinguished genetics scientists.

Beginning in 2001, the Prize a gold medal and unrestricted $500,000 cash award has been awarded for fundamental insights in the field of genetics. These may include original discoveries in genetic function, regulation, transmission, and variation, as well as in genomic organization.

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Learn Genetics Visually in 24 Hours by Rapid Learning

Thursday, August 4th, 2016

With our breakthrough 24x Rapid Learning SystemTM of smart teaching and rich media, you can now finally gain a powerful learning edge over others who are still struggling with static textbooks and online freebies. Catch up and excel in class with the host of tightly integrated learning modules, designed specifically for today's web and video savvy students and supported by a team of teaching experts. Speed up your learning one chapter one hour at a time. The entire 24-chapter rapid learning package includes:

Genetics -Tutorial Series

This series provides an in-depth coverage of a typical genetics curriculum with rich-media and expert narration for rapid mastery.

Core Unit #1 The Introduction

Core Unit #2 Cellular Basis of Genetics

Core Unit #3 Genetic Mapping

Core Unit #4 Quantitative Genetics

Core Unit #5 Molecular Genetics

Core Unit #6 Recombinant DNA Technology

Core Unit #7 Mutation and Disease

Core Unit #8 Developmental, Population and Evolutionary Genetics

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Interdepartmental Genetics Program | Kansas State University

Thursday, August 4th, 2016

Interdepartmental Genetics Program New Graduate Funding Opportunities! The Interdepartmental Genetics Program is now offering a competitive fellowship to select applicants to its PhD program. This prestigious fellowship comes with anannual stipend of$29,400plus tuition (2015-2016 academic year rate), and allows students to rotate through multiple Genetics research labs before choosing a thesis advisor. Submit your applications soon, its deadline isDecember15, 2015.More information

The goal of the interdepartmental Genetics Graduate Program at Kansas State University is to train M.S. and Ph.D. students in the basic principles and applications of classical and molecular genetics for careers in research, teaching, and industry. The program is diverse and includes faculty from the following Divisions and Departments

As a result, research opportunities are diverse and include plant and animal breeding, population and evolutionary genetics, quantitative genetics, molecular and developmental genetics, and genomics and bioinformatics. Interdisciplinary interactions are fostered and encouraged based upon a common interest in genetics. Such interactions often bridge basic and applied genetics and merge diverse fields such as agriculture and computer sciences. Thus, the Genetics Graduate Program offers students a truly interdisciplinary and interactive environment in which to pursue their scientific interests.

After meeting the core curriculum requirements, students in the program are encouraged to choose an emphasis, which enables them to specialize in a particular subdiscipline of genetics. At present, the following emphases are available: Arthropod Genetics; Genetics of Plant-Microbe Interactions; Molecular, Cellular, and Developmental Genetics; and Quantitative Genetics. These tracks have been designed so that there is significant overlap in coursework.

Research and teaching facilities at Kansas State University are excellent. These include theIntegrated GenomicsFacility(IGF), the Plant Biotechnology Center, Sequencing and Genotyping Facility, NMR Facility, Metabolomics Center, electron microscopes, real-time PCR machines, insectaries, greenhouses, etc. The interdisciplinary nature of our programs provides access to many of these facilities to all students in the program. High-technology classrooms with state-of-the-art computer technology are also available.

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Interdepartmental Genetics Program | Kansas State University

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Introduction to genetics – Wikipedia, the free encyclopedia

Thursday, August 4th, 2016

This article is a non-technical introduction to the subject. For the main encyclopedia article, see Genetics.

A long molecule that looks like a twisted ladder. It is made of four types of simple units and the sequence of these units carries information, just as the sequence of letters carries information on a page.

They form the rungs of the DNA ladder and are the repeating units in DNA. There are four types of nucleotides (A, T, G and C) and it is the sequence of these nucleotides that carries information.

A package for carrying DNA in the cells. They contain a single long piece of DNA that is wound up and bunched together into a compact structure. Different species of plants and animals have different numbers and sizes of chromosomes.

A segment of DNA. Genes are like sentences made of the "letters" of the nucleotide alphabet, between them genes direct the physical development and behavior of an organism. Genes are like a recipe or instruction book, providing information that an organism needs so it can build or do something - like making an eye or a leg, or repairing a wound.

The different forms of a given gene that an organism may possess. For example, in humans, one allele of the eye-color gene produces green eyes and another allele of the eye-color gene produces brown eyes.

The complete set of genes in a particular organism.

When people change an organism by adding new genes, or deleting genes from its genome.

An event that changes the sequence of the DNA in a gene.

Genetics is the study of genes what they are, what they do, and how they work. Genes are made up of molecules inside the nucleus of a cell that are strung together in such a way that the sequence carries information: that information determines how living organisms inherit phenotypic traits, (features) determined by the genes they received from their parents and thereby going back through the generations. For example, offspring produced by sexual reproduction usually look similar to each of their parents because they have inherited some of each of their parents' genes. Genetics identifies which features are inherited, and explains how these features pass from generation to generation. In addition to inheritance, genetics studies how genes are turned on and off to control what substances are made in a cell - gene expression; and how a cell divides - mitosis or meiosis.

Some phenotypic traits can be seen, such as eye color while others can only be detected, such as blood type or intelligence. Traits determined by genes can be modified by the animal's surroundings (environment): for example, the general design of a tiger's stripes is inherited, but the specific stripe pattern is determined by the tiger's surroundings. Another example is a person's height: it is determined by both genetics and nutrition.

Genes are made of DNA, which is divided into separate pieces called chromosomes. Humans have 46: 23 pairs, though this number varies between species, for example many primates have 24 pairs. Meiosis creates special cells, sperm in males and eggs in females, which only have 23 chromosomes. These two cells merge into one during the fertilization stage of sexual reproduction, creating a zygote in which a nucleic acid double helix divides, with each single helix occupying one of the daughter cells, resulting in half the normal number of genes. The zygote then divides into four daughter cells by which time genetic recombination has created a new embryo with 23 pairs of chromosomes, half from each parent. Mating and resultant mate choice result in sexual selection. In normal cell division (mitosis) is possible when the double helix separates, and a complement of each separated half is made, resulting in two identical double helices in one cell, with each occupying one of the two new daughter cells created when the cell divides.

Chromosomes all contain four nucleotides, abbreviated C (cytosine), G (guanine), A (adenine), or T (thymine), which line up in a particular sequence and make a long string. There are two strings of nucleotides coiled around one another in each chromosome: a double helix. C on one string is always opposite from G on the other string; A is always opposite T. There are about 3.2 billion nucleotide pairs on all the human chromosomes: this is the human genome. The order of the nucleotides carries genetic information, whose rules are defined by the genetic code, similar to how the order of letters on a page of text carries information. Three nucleotides in a row - a triplet - carry one unit of information: a codon.

The genetic code not only controls inheritance: it also controls gene expression, which occurs when a portion of the double helix is uncoiled, exposing a series of the nucleotides, which are within the interior of the DNA. This series of exposed triplets (codons) carries the information to allow machinery in the cell to "read" the codons on the exposed DNA, which results in the making of RNA molecules. RNA in turn makes either amino acids or microRNA, which are responsible for all of the structure and function of a living organism; i.e. they determine all the features of the cell and thus the entire individual. Closing the uncoiled segment turns off the gene.

Heritability means the information in a given gene is not always exactly the same in every individual in that species, so the same gene in different individuals does not give exactly the same instructions. Each unique form of a single gene is called an allele; different forms are collectively called polymorphisms. As an example, one allele for the gene for hair color and skin cell pigmentation could instruct the body to produce black pigment, producing black hair and pigmented skin; while a different allele of the same gene in a different individual could give garbled instructions that would result in a failure to produce any pigment, giving white hair and no pigmented skin: albinism. Mutations are random changes in genes creating new alleles, which in turn produce new traits, which could help, harm, or have no new effect on the individual's likelihood of survival; thus, mutations are the basis for evolution.

Genes are pieces of DNA that contain information for synthesis of ribonucleic acids (RNAs) or polypeptides. Genes are inherited as units, with two parents dividing out copies of their genes to their offspring. This process can be compared with mixing two hands of cards, shuffling them, and then dealing them out again. Humans have two copies of each of their genes, and make copies that are found in eggs or spermbut they only include one copy of each type of gene. An egg and sperm join to form a complete set of genes. The eventually resulting offspring has the same number of genes as their parents, but for any gene one of their two copies comes from their father, and one from their mother.[1]

The effects of this mixing depend on the types (the alleles) of the gene. If the father has two copies of an allele for red hair, and the mother has two copies for brown hair, all their children get the two alleles that give different instructions, one for red hair and one for brown. The hair color of these children depends on how these alleles work together. If one allele dominates the instructions from another, it is called the dominant allele, and the allele that is overridden is called the recessive allele. In the case of a daughter with alleles for both red and brown hair, brown is dominant and she ends up with brown hair.[2]

Although the red color allele is still there in this brown-haired girl, it doesn't show. This is a difference between what you see on the surface (the traits of an organism, called its phenotype) and the genes within the organism (its genotype). In this example you can call the allele for brown "B" and the allele for red "b". (It is normal to write dominant alleles with capital letters and recessive ones with lower-case letters.) The brown hair daughter has the "brown hair phenotype" but her genotype is Bb, with one copy of the B allele, and one of the b allele.

Now imagine that this woman grows up and has children with a brown-haired man who also has a Bb genotype. Her eggs will be a mixture of two types, one sort containing the B allele, and one sort the b allele. Similarly, her partner will produce a mix of two types of sperm containing one or the other of these two alleles. When the transmitted genes are joined up in their offspring, these children have a chance of getting either brown or red hair, since they could get a genotype of BB = brown hair, Bb = brown hair or bb = red hair. In this generation, there is therefore a chance of the recessive allele showing itself in the phenotype of the children - some of them may have red hair like their grandfather.[2]

Many traits are inherited in a more complicated way than the example above. This can happen when there are several genes involved, each contributing a small part to the end result. Tall people tend to have tall children because their children get a package of many alleles that each contribute a bit to how much they grow. However, there are not clear groups of "short people" and "tall people", like there are groups of people with brown or red hair. This is because of the large number of genes involved; this makes the trait very variable and people are of many different heights.[3] Despite a common misconception, the green/blue eye traits are also inherited in this complex inheritance model.[4] Inheritance can also be complicated when the trait depends on interaction between genetics and environment. For example, malnutrition does not change traits like eye color, but can stunt growth.[5]

Some diseases are hereditary and run in families; others, such as infectious diseases, are caused by the environment. Other diseases come from a combination of genes and the environment.[6]Genetic disorders are diseases that are caused by a single allele of a gene and are inherited in families. These include Huntington's disease, Cystic fibrosis or Duchenne muscular dystrophy. Cystic fibrosis, for example, is caused by mutations in a single gene called CFTR and is inherited as a recessive trait.[7]

Other diseases are influenced by genetics, but the genes a person gets from their parents only change their risk of getting a disease. Most of these diseases are inherited in a complex way, with either multiple genes involved, or coming from both genes and the environment. As an example, the risk of breast cancer is 50 times higher in the families most at risk, compared to the families least at risk. This variation is probably due to a large number of alleles, each changing the risk a little bit.[8] Several of the genes have been identified, such as BRCA1 and BRCA2, but not all of them. However, although some of the risk is genetic, the risk of this cancer is also increased by being overweight, drinking a lot of alcohol and not exercising.[9] A woman's risk of breast cancer therefore comes from a large number of alleles interacting with her environment, so it is very hard to predict.

The function of genes is to provide the information needed to make molecules called proteins in cells.[1] Cells are the smallest independent parts of organisms: the human body contains about 100 trillion cells, while very small organisms like bacteria are just one single cell. A cell is like a miniature and very complex factory that can make all the parts needed to produce a copy of itself, which happens when cells divide. There is a simple division of labor in cells - genes give instructions and proteins carry out these instructions, tasks like building a new copy of a cell, or repairing damage.[10] Each type of protein is a specialist that only does one job, so if a cell needs to do something new, it must make a new protein to do this job. Similarly, if a cell needs to do something faster or slower than before, it makes more or less of the protein responsible. Genes tell cells what to do by telling them which proteins to make and in what amounts.

Proteins are made of a chain of 20 different types of amino acid molecules. This chain folds up into a compact shape, rather like an untidy ball of string. The shape of the protein is determined by the sequence of amino acids along its chain and it is this shape that, in turn, determines what the protein does.[10] For example, some proteins have parts of their surface that perfectly match the shape of another molecule, allowing the protein to bind to this molecule very tightly. Other proteins are enzymes, which are like tiny machines that alter other molecules.[11]

The information in DNA is held in the sequence of the repeating units along the DNA chain.[12] These units are four types of nucleotides (A,T,G and C) and the sequence of nucleotides stores information in an alphabet called the genetic code. When a gene is read by a cell the DNA sequence is copied into a very similar molecule called RNA (this process is called transcription). Transcription is controlled by other DNA sequences (such as promoters), which show a cell where genes are, and control how often they are copied. The RNA copy made from a gene is then fed through a structure called a ribosome, which translates the sequence of nucleotides in the RNA into the correct sequence of amino acids and joins these amino acids together to make a complete protein chain. The new protein then folds up into its active form. The process of moving information from the language of RNA into the language of amino acids is called translation.[13]

If the sequence of the nucleotides in a gene changes, the sequence of the amino acids in the protein it produces may also change - if part of a gene is deleted, the protein produced is shorter and may not work any more.[10] This is the reason why different alleles of a gene can have different effects in an organism. As an example, hair color depends on how much of a dark substance called melanin is put into the hair as it grows. If a person has a normal set of the genes involved in making melanin, they make all the proteins needed and they grow dark hair. However, if the alleles for a particular protein have different sequences and produce proteins that can't do their jobs, no melanin is produced and the person has white skin and hair (albinism).[14]

Genes are copied each time a cell divides into two new cells. The process that copies DNA is called DNA replication.[12] It is through a similar process that a child inherits genes from its parents, when a copy from the mother is mixed with a copy from the father.

DNA can be copied very easily and accurately because each piece of DNA can direct the creation of a new copy of its information. This is because DNA is made of two strands that pair together like the two sides of a zipper. The nucleotides are in the center, like the teeth in the zipper, and pair up to hold the two strands together. Importantly, the four different sorts of nucleotides are different shapes, so for the strands to close up properly, an A nucleotide must go opposite a T nucleotide, and a G opposite a C. This exact pairing is called base pairing.[12]

When DNA is copied, the two strands of the old DNA are pulled apart by enzymes; then they pair up with new nucleotides and then close. This produces two new pieces of DNA, each containing one strand from the old DNA and one newly made strand. This process is not predictably perfect as proteins attach to a nucleotide while they are building and cause a change in the sequence of that gene. These changes in DNA sequence are called mutations.[15] Mutations produce new alleles of genes. Sometimes these changes stop the functioning of that gene or make it serve another advantageous function, such as the melanin genes discussed above. These mutations and their effects on the traits of organisms are one of the causes of evolution.[16]

A population of organisms evolves when an inherited trait becomes more common or less common over time.[16] For instance, all the mice living on an island would be a single population of mice: some with white fur, some gray. If over generations, white mice became more frequent and gray mice less frequent, then the color of the fur in this population of mice would be evolving. In terms of genetics, this is called an increase in allele frequency.

Alleles become more or less common either by chance in a process called genetic drift, or by natural selection.[17] In natural selection, if an allele makes it more likely for an organism to survive and reproduce, then over time this allele becomes more common. But if an allele is harmful, natural selection makes it less common. In the above example, if the island were getting colder each year and snow became present for much of the time, then the allele for white fur would favor survival, since predators would be less likely to see them against the snow, and more likely to see the gray mice. Over time white mice would become more and more frequent, while gray mice less and less.

Mutations create new alleles. These alleles have new DNA sequences and can produce proteins with new properties.[18] So if an island was populated entirely by black mice, mutations could happen creating alleles for white fur. The combination of mutations creating new alleles at random, and natural selection picking out those that are useful, causes adaptation. This is when organisms change in ways that help them to survive and reproduce.

Since traits come from the genes in a cell, putting a new piece of DNA into a cell can produce a new trait. This is how genetic engineering works. For example, rice can be given genes from a maize and a soil bacteria so the rice produces beta-carotene, which the body converts to Vitamin A.[19] This can help children suffering from Vitamin A deficiency. Another gene being put into some crops comes from the bacterium Bacillus thuringiensis; the gene makes a protein that is an insecticide. The insecticide kills insects that eat the plants, but is harmless to people.[20] In these plants, the new genes are put into the plant before it is grown, so the genes are in every part of the plant, including its seeds.[21] The plant's offspring inherit the new genes, which has led to concern about the spread of new traits into wild plants.[22]

The kind of technology used in genetic engineering is also being developed to treat people with genetic disorders in an experimental medical technique called gene therapy.[23] However, here the new gene is put in after the person has grown up and become ill, so any new gene is not inherited by their children. Gene therapy works by trying to replace the allele that causes the disease with an allele that works properly.

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