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Largest-ever genetic study of epilepsy finds possible therapeutic targets - Medical Xpress
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23andMe is on the brink. What happens to all its DNA data? - NPR
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Gene Activity in Depression Linked to Immune System and Inflammation - Neuroscience News
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Genetics and AI Help Patients with Early Detection of Breast Cancer Risk - Adventist Review
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23andMe Is Sinking Fast. Can the Company Survive? - WIRED
Genetic variations in remote UK regions linked to higher disease risk Medical Xpress
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Genetics Definition
Genetics is the study of genes and inheritance in living organisms. This branch of science has a fascinating history, stretching from the 19th century when scientists began to study how organisms inherited traits from their parents, to the present day when we can read the source code of living things letter-by-letter.
Genetics started out with curiosity about why things are the way things are why do children resemble one parent more than another? Why do some species resemble each other more closely than others?
It has evolved into an almost universal answer handbook for biology. By reading the source code or blueprint for an organism, scientists today are often able to pinpoint exactly where an organism came from, how it has changed over time, what diseases it might develop, and how its life processes are similar to or different from those of other organisms.
In the 19th century, it was known that offspring resemble their parents but almost nothing was known about why this happened. Why did some children take after one parent, but not the other. Why could plants and animals have offspring that had traits seen in neither parent? Why did some species resemble each other more closely than others?
In the 19th century, Gregor Mendel began examining inheritance in a systematic way by breeding pea plants. He tracked several traits of pea plants across several generations, recording what kinds of parents had what kinds off offspring. He successfully derived the mathematics behind dominant and recessive genes the first empirical evidence that traits really were passed down in some measurable way from parent to offspring.
The image below shows a Punnett square of Mendels pea plants. The Punnett square was developed by English geneticist Reginald Punnett to visually represent how dominant and recessive traits were passed to offspring. The math yielded by the Punnett square matched the results Mendel found in his hands-on studies of pea plants.
Around the same time, Charles Darwin was writing The Origin of Species, after examining changes in the traits if island finches during times of drought and plenty. Darwin concluded that finches which had the traits best-suited for survival were most likely to survive to pass those traits on, yielding changes in the traits of the overall population over time.
His work, when taken together with Mendels, began to suggest that all species on Earth might be related to each other, and might have gradually drifted apart by inheriting different traits through natural selection.
From there, the field of genetics advanced slowly. By the early 20th century, scientists using light microscopes powerful enough to see into a cells nucleus suspected that chromosomes were the seat of genetic information. They were able to connect chromosomal inheritance to trait inheritance, proving that the instructions for inherited traits were carried on chromosomes within the nucleus of eukaryotic cells.
The next great break in genetics started in the late 20th century, when the technology to read the nucleotide source code of the genome began to become available. Since then, the technology has gotten faster, more affordable, and more accurate allowing scientists to sequence the whole genomes of many organisms and compare them.
The ability to read the source code of life has led to a revolution in the way we think about and classify organisms.
Prior to the advent of gene sequencing, scientists guessed at organisms relationships to each other by studying their physical characteristics. Organisms with similar characteristics were often assumed to be related even though many examples were known of convergent evolution, where two unrelated organisms evolve the same traits separately.
With the advent of gene sequencing and molecular genetics- referring to the ability to read the DNA molecule at the molecular level- it became possible to trace descent lineages directly. Scientists can now read a cells source code and determine at where, and roughly when, an organisms genome changed.
As a result, a great deal of material that was taught in schools as recently as ten years ago is now known to be incomplete. Archaea and bacteria once classified in the same kingdom are now known to be genetically quite different from each other. Fungi are now known to be more closely related to animals than plants. Many other fantastically weird and fascinating discoveries have come out of the genome revolution each one bringing us a step closer to understanding what makes us who we are, and how we are interconnected.
Gene sequencing has also led to a revolution in the way we think about, diagnose, and treat disease. In many cases, its now possible to know how likely a person is to get a given disease based on looking at their genome.
Scientists hope that this will lead to great revolutions in medicine in the centuries to come as medicine catches up to genetics, it may someday be possible to determine what medications will work best on a disease, or what lifestyle changes will keep a person healthy, simply by reading their DNA.
This has also led to new ethical and economic challenges.
Some women whose genes have certain mutation of the BRCA1/2 gene, for example, opt to have their breasts and ovaries removed even if they are healthy because they know there is a high chance that they will develop cancer in these organs.
In 2013, Angelina Jolie made headlines by going public with her choice to have her own breasts removed after finding out through a genetic test that she had an 87% chance of some day acquiring breast cancer.
In other cases, geneticists can tell people that they will develop a serious disease but do not yet have the tools to stop it from happening. People in families with Huntingtons disease, for example, can find out if they have the gene for this devastating and inevitably fatal dementia. But what can they do with this information?
An unexpected economic challenge has come from health insurance companies. Insurance companies have always made their money by gambling on who was likely to get sick and who wasnt. Now that the tools exist for companies to find out who is more likely to get sick at a very fine level of detail, concerns have been raised that people with unhealthy genes might be charged much more for health insurance than people with healthy genes.
1. Which of the following was NOT known when Gregor Mendel began his studies?A. That offspring tended to resemble their parentsB. That parents sometimes had offspring who didnt look like either of themC. That some traits are dominant and some are recessiveD. None of the above
Answer to Question #1
C is correct. Mendel developed the theory of dominant and recessive genes after carefully studying the pattern of inheritance of traits among pea plants over several generations.
2. Which of the following was NOT a reason for misclassifying many organisms prior to the advent of molecular genetics?A. The organisms looked similar under the microscopeB. The organisms had evolved similar traitsC. Scientists were unable to read the organisms source codes and had to work off of superficial characteristicsD. Scientists of the past were less intelligent than scientists of today
Answer to Question #2
D is correct. Scientists of the past were incredibly innovative, designing experiments that yielded brilliant insights with very limited tools. But without the ability to read an organisms genetic code, they were restricted to making guesses about how to classify organisms based on their superficial characteristics.
3. Which of the following is NOT a possibility as genetic science advances?A. It may become possible to replace unhealthy genes with healthy genes, if a safe genetic engineering vector for humans is developed.B. It may become possible to choose the best medication for a disease right away based on the diseases genetic profile.C. Laws may need to be passed ensuring that people with genes for certain illnesses are protected from discrimination and have access to healthcare.D. None of the above.
Answer to Question #3
D is correct. All of these are possibilities for the next century, as scientists continue to learn more about genes and how to work with them!
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Genetics - Definition, History and Impact | Biology Dictionary
gene, unit of hereditary information that occupies a fixed position (locus) on a chromosome. Genes achieve their effects by directing the synthesis of proteins.
In eukaryotes (such as animals, plants, and fungi), genes are contained within the cell nucleus. The mitochondria (in animals) and the chloroplasts (in plants) also contain small subsets of genes distinct from the genes found in the nucleus. In prokaryotes (organisms lacking a distinct nucleus, such as bacteria), genes are contained in a single chromosome that is free-floating in the cell cytoplasm. Many bacteria also contain plasmidsextrachromosomal genetic elements with a small number of genes.
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The number of genes in an organisms genome (the entire set of chromosomes) varies significantly between species. For example, whereas the human genome contains an estimated 20,000 to 25,000 genes, the genome of the bacterium Escherichia coli O157:H7 houses precisely 5,416 genes. Arabidopsis thalianathe first plant for which a complete genomic sequence was recoveredhas roughly 25,500 genes; its genome is one of the smallest known to plants. Among extant independently replicating organisms, the bacterium Mycoplasma genitalium has the fewest number of genes, just 517.
A brief treatment of genes follows. For full treatment, see heredity.
Genes are composed of deoxyribonucleic acid (DNA), except in some viruses, which have genes consisting of a closely related compound called ribonucleic acid (RNA). A DNA molecule is composed of two chains of nucleotides that wind about each other to resemble a twisted ladder. The sides of the ladder are made up of sugars and phosphates, and the rungs are formed by bonded pairs of nitrogenous bases. These bases are adenine (A), guanine (G), cytosine (C), and thymine (T). An A on one chain bonds to a T on the other (thus forming an AT ladder rung); similarly, a C on one chain bonds to a G on the other. If the bonds between the bases are broken, the two chains unwind, and free nucleotides within the cell attach themselves to the exposed bases of the now-separated chains. The free nucleotides line up along each chain according to the base-pairing ruleA bonds to T, C bonds to G. This process results in the creation of two identical DNA molecules from one original and is the method by which hereditary information is passed from one generation of cells to the next.
The sequence of bases along a strand of DNA determines the genetic code. When the product of a particular gene is needed, the portion of the DNA molecule that contains that gene will split. Through the process of transcription, a strand of RNA with bases complementary to those of the gene is created from the free nucleotides in the cell. (RNA has the base uracil [U] instead of thymine, so A and U form base pairs during RNA synthesis.) This single chain of RNA, called messenger RNA (mRNA), then passes to the organelles called ribosomes, where the process of translation, or protein synthesis, takes place. During translation, a second type of RNA, transfer RNA (tRNA), matches up the nucleotides on mRNA with specific amino acids. Each set of three nucleotides codes for one amino acid. The series of amino acids built according to the sequence of nucleotides forms a polypeptide chain; all proteins are made from one or more linked polypeptide chains.
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Experiments conducted in the 1940s indicated one gene being responsible for the assembly of one enzyme, or one polypeptide chain. This is known as the one geneone enzyme hypothesis. However, since this discovery, it has been realized that not all genes encode an enzyme and that some enzymes are made up of several short polypeptides encoded by two or more genes.
Experiments have shown that many of the genes within the cells of organisms are inactive much or even all of the time. Thus, at any time, in both eukaryotes and prokaryotes, it seems that a gene can be switched on or off. The regulation of genes between eukaryotes and prokaryotes differs in important ways.
The process by which genes are activated and deactivated in bacteria is well characterized. Bacteria have three types of genes: structural, operator, and regulator. Structural genes code for the synthesis of specific polypeptides. Operator genes contain the code necessary to begin the process of transcribing the DNA message of one or more structural genes into mRNA. Thus, structural genes are linked to an operator gene in a functional unit called an operon. Ultimately, the activity of the operon is controlled by a regulator gene, which produces a small protein molecule called a repressor. The repressor binds to the operator gene and prevents it from initiating the synthesis of the protein called for by the operon. The presence or absence of certain repressor molecules determines whether the operon is off or on. As mentioned, this model applies to bacteria.
The genes of eukaryotes, which do not have operons, are regulated independently. The series of events associated with gene expression in higher organisms involves multiple levels of regulation and is often influenced by the presence or absence of molecules called transcription factors. These factors influence the fundamental level of gene control, which is the rate of transcription, and may function as activators or enhancers. Specific transcription factors regulate the production of RNA from genes at certain times and in certain types of cells. Transcription factors often bind to the promoter, or regulatory region, found in the genes of higher organisms. Following transcription, introns (noncoding nucleotide sequences) are excised from the primary transcript through processes known as editing and splicing. The result of these processes is a functional strand of mRNA. For most genes this is a routine step in the production of mRNA, but in some genes there are multiple ways to splice the primary transcript, resulting in different mRNAs, which in turn result in different proteins. Some genes also are controlled at the translational and posttranslational levels.
Mutations occur when the number or order of bases in a gene is disrupted. Nucleotides can be deleted, doubled, rearranged, or replaced, each alteration having a particular effect. Mutation generally has little or no effect, but, when it does alter an organism, the change may be lethal or cause disease. A beneficial mutation will rise in frequency within a population until it becomes the norm.
For more information on the influence of genetic mutations in humans and other organisms, see human genetic disease and evolution.
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Gene | Definition, Structure, Expression, & Facts | Britannica