StemCell Therapy

Cells are the bodys building blocks. Many different types of cells havedifferent functions. They make up all of your bodys organs and tissues. Nearlyevery cell in a persons body has the same deoxyribonucleic acid, or DNA. DNA isthe hereditary material in humans and almost all other organisms. Most DNA is located inthe cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also befound in the mitochondria (where it is called mitochondrial DNA).

DNA contains the code for building and maintaining an organism. The code is spelled outin the order, or sequence, of four chemical basesadenine (A), cytosine (C),guanine (G), and thymine (T)in the same way that letters of the alphabet cometogether to form words, sentences, and paragraphs. Human DNA consists of about threebillion bases, and more than 99 percent of those bases are the same in all people.

DNA bases pair with each otherA with T, C with Gto form units calledbase pairs. Each base is attached to a sugar molecule and a phosphate molecule.Together, base, sugar, and phosphate are called a nucleotide. Nucleotides are arrangedin two long strands that form a spiral called a double helix. The structure of thedouble helix is like a ladder, with base pairs running through the middle like rungs andsugar and phosphate molecules along the outside.

Genes are small sections of the long chain of DNA. They are the basic physical andfunctional units of heredity. In humans, genes vary in size from a few hundred DNA basesto more than two million bases. The Human Genome Project has estimated that humans havebetween 20,000 and 25,000 genes. Every person has two copies of each gene, one inheritedfrom each parent. Most genes are the same in all people, but a small number of genes(less than one percent of the total) are slightly different between people. Alleles areforms of the same gene with small differences in their sequence of DNA bases. Thesesmall differences contribute to each persons unique features.

Genes act as instructions to make molecules called proteins. To function correctly, eachcell depends on thousands of proteins to do their jobs in the right places at the righttimes. Sometimes changes in a gene, called mutations, prevent one or more of theseproteins from working properly. This may cause cells or organs to change or lose theirfunction, which can lead to a disease. Mutations, rather than genes themselves, causedisease. For example, when people say that someone has the cystic fibrosisgene, they are usually referring to a mutated version of the CFTR gene, whichcauses the disease. All people, including those without cystic fibrosis, have a versionof the CFTR gene.

Sections of DNA form genes, and many genes together form chromosomes. People inherit twosets of chromosomes (one from each parent), which is why every person has two copies ofeach gene. Humans have 23 pairs of chromosomes.

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BASIC GENETICS INFORMATION - Understanding Genetics - NCBI Bookshelf

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