- The twisted-ladder shape that two linear strands of DNA assume when complementary nucleotides on opposing strands bond together.
Definition from: Human Genome Project Information
at the U.S. Department of Energy
- Double helix is the description of the structure of a DNA molecule. A DNA molecule consists of two strands that wind around each other like a twisted ladder. Each strand has a backbone made of alternating groups of sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G), or thymine (T). The two strands are held together by bonds between the bases, adenine forming a base pair with thymine, and cytosine forming a base pair with guanine.
Definition from: Talking Glossary of Genetic Terms from the National Human Genome Research Institute
Related discussion in the Handbook
See also Understanding Medical Terminology.