The ABCs of Genes
Remember Watson and Crick? The Viral detectives who first discovered DNA (deoxyribonucleic acid), the source of our being? They provided the basics, which still hold true today.

Genes store the information necessary for creating a living organism. The information is stored in the form of DNA organized into structures called chromosomes. Apart from sex cells (eggs and sperm) and mature blood cells, every cell in the body contains 23 pairs of chromosomes. One of each pair is inherited from the mother, the other from the father. Each chromosome is a packet of compressed and convoluted DNA. Genes are sections of DNA containing the blueprint for the whole body, including such minuscule specific details as what kind of chemokine receptors cells will have.

Watson and Crick found that DNA is made up of a double-stranded helix held together by hydrogen bonds between specific pairs of bases. The four protein bases, A, T, G, and C (adenine, thymine, guanine, and cytosine) bond with each other in fixed and complimentary patterns that give us our individuality. A switch in these letters-replacing adenine for thymine, for example-alters the pattern. Genetic mutations are caused by these alterations.

If a gene is thought of as a sentence, and DNA code as letters, a mutation may affect only one letter, but that can affect the information it gives the cell. DNA letters are called nucleotides and are stored in long sequences that can be "read" by researchers-aided by supersophisticated computers. To get an idea of what it takes to read a gene, consider that we humans have about 3.2 billion of these base pair DNA letters, which make up about 50,000-100,000 genes. Since each strand of DNA is composed of identical bases, genetic maps and tests that compare DNA are very accurate. There are about a million differences between your 3.2-billion-letter DNA alphabet and that of another person.

-RJ, ACD.