Biology Reference
In-Depth Information
Figure 16.6.
Hydrogen bond.
16.3 Deoxyribonucleic Acid
A DNA (deoxyribonucleic acid) molecule formed by two polynu-
cleotide chains consists of nucleotide subunits. There are four types
of nucleotide subunits of DNA, which are composed of deoxyribose
attached to phosphate groups and four bases: adenosine (A),
cytosine (C), guanine (G), and thymine (T). These nucleotides are
covalentlyboundtoeachotherviathedeoxyriboseandphosphates.
One end of the polynucleotide chain has 3' hydroxyl and the other
end has 5' phosphate.
The two chains form double helix as two sugar-phosphate
backbones wind around each other as three-dimensional structure.
The bases are stacked inside the helix and their hydrophobic
structures are very close to each other, whereas the hydrophilic
