Table of Contents
Deoxyribonucleic Acid Definition
DNA – the abbreviation for deoxyribonucleic acid. DNA is the molecule of heredity; its sequences form the body’s GENETIC CODE. Each cell in the body contains DNA within the chromosomes in its nucleus (except erythrocytes, which do not have nuclei). DNA has a characteristic double-helix structure that resembles a gently twisting ladder. The supporting rails of this structure are deoxyribose, a sugar-phosphate, and the crossbands are nitrogen bases: adenine (A), thymine (T), guanine (G), and cytosine (C). These bases pair in precise, predictable patterns arranged in nearly endless combinations, more than three billion in all.
British scientists James Watson and Francis Crick unraveled the double-helix structure of DNA in 1953, identifying its two spiraling, sugar–phosphate (deoxyribose) supports and cross-bands of paired nucleic acids. Just 50 years later researchers involved with the HUMAN GENOME PROJECT concluded their mapping of the human GENOME, which included determining the entire biochemical sequence of human DNA. Chromosomes are structures of DNA, and genes are segments of chromosomes (also made up of DNA).
For further discussion of DNA within the context of the structures and functions of genetics, please see the overview section “Genetics and Molecular Medicine.”