Genetics / Chemistry of the Gene / Nucleic Acids and Their Structure
Bases
Fig. 25.8. Numbering of carbon atoms in a pyridine ring.
Fig. 25.9. Structure of different pyrimidines.
Fig. 25.10. Structure of two purines.
The bases are of two types namely- (i)
pyrimidines and
(ii) purines. The pyrimidine ring can be numbered in two different manners (Fig. 25.8). Only the old numbering system will be followed in this book. There are three main pyrimidine bases found in nucleic acid, namely
thymine, cytosine and
uracil (Fig. 25.9). While cytosine and thymine are commonly found in DNA, cytosine and uracil are found in RNA. In RNA, thymine is replaced by uracil. Similarly, there are two main purine bases,
adenine and
guanine (Fig. 25.10).
Support our developers
More in this section
