A complex of nucleoproteins (chiefly DNA) that is the active transmitter of genetic information. Each of the body's 50,000 to 100,000 genes contains the code for a specific product, typically, a protein such as an enzyme.Genes occur on the chromosomes of every living cell, where they are arranged in a linear order. Genetic mechanism is the same in all organisms, ranging from the lowest forms of life, both plant and animal, to humans. Every organism has a large number of different genes; there are over 10,000 in each cell of the human body. These control the intricate and well-balanced system of biochemical reactions in the cell. The first synthesis of a gene was reported in 1970. In 1976, it was announced that a synthetic gene was successfully introduced into a microorganism in which it functioned in the same manner as would a normal gene. Because of the ability of DNA to store and transfer coded genetic instructions, genes determine the sequence of amino acids in specific polypeptides (see proteins), thus they prescribe the structure of the proteins synthesized. In viruses, the genes consist of ribonucleic acid (RNA). Mutation of genes is a change in the basic sequence of amino acids in DNA and may be induced by ionizing radiation. Mutations can occur in any living cell.See Genetic Code; Radiation, Ionizing; Recombinant DNA Molecules; Molecular Biology.
