DNA stands for deoxyribonucleic acid which is a
structure of sugar, phosphate and a base combined
into a complex double helix. The two strands in
the helix are complementary to each other, which
means that each DNA strand contains the template
information for synthesis of a new copy of the other
The building blocks of DNA are the 5-carbon sugar
deoxyribose linked together by phosphodiester
bonds forming two strands of sugar-phosphate backbones
on the outside of the double helix. Each ribose
also binds one of four alternative bases: adenine
(A), guanine (G), cytosine (C) or thymine (T).
opposing strands are held together by basepairing
between the two strands: G is always paired with
C by three hydrogen bonds and A is always paired
with T by two hydrogen bonds.