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Article: Double Helix
- Article from:
- Chemistry: Foundations and Applications
- Author:
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Double Helix
Described in 1953 by James Watson and Francis Crick, the double helix of
DNA
(deoxyribonucleic acid) is the cellular storehouse of genetic information. This biopolymer consists of a pair of complementary chains approximately 2.4 nanometers (9.5
×
10
−
8
inches) in diameter and composed of
deoxyribose sugar molecules linked to each other by phosphoric acid, connecting the number three carbon of one sugar to the number five carbon of another. Attached to each sugar is a heterocyclic base:
adenine
,
guanine
,
cytosine
, or
thymine
. Each turn of the helix contains about 10.4 nucleotides.
These chains are said to be complementary: Guanine on one chain always ...