There are 22 numbered chromosomes, plus two that determine gender, X and Y. A female has two X chromosomes, while a male has an X and a Y. A human normally has 23 pairs of chromosomes. A complete human genome is contained in a coiled double helix of DNA, or deoxyribonucleic acid. A human hair is about 50 microns wide. About 3 billion DNA subunits, called base-pairs, make up the double helix. Most of the base-pairs of DNA between genes have no known function.
Genes give coded instructions to the cell on how to assemble proteins.
Many human disorders are caused by genetic flaws, or by the absence of one or more genes. Produced by Newsday Electronic Publishing.