Question

Purine and pyrimidine nitrogen bases respectively are

• A. A,T and G, C,U
• B. A, C, T and G, U
• C. A, G and C, T, U
• D. A, G, T and C, U

Answer 1

The correct option is C A, G and C, T, U

There are two kinds of nitrogen-containing bases: purines and pyrimidines. Purines consist of a six-membered and a five-membered nitrogen-containing ring, fused together. Pyridmidines have only a six-membered nitrogen-containing ring. There are 2 purines and 3 pyrimidines.

Purines: Adenine (A) = 6-amino purine and Guanine (G) = 2-amino-6-oxy purine. Adenine and guanine are found in both DNA and RNA.

Pyrimidines: Uracil (U) = 2,4-dioxy pyrimidine; Thymine (T) = 2,4-dioxy-5-methyl pyrimidine; Cytosine (C) = 2-oxy-4-amino pyrimidine. Cytosine is found in both DNA and RNA. Uracil is found only in RNA. Thymine is normally found in DNA.