Question

Identify the group which contains only pyrimidines.

• A. Adenine, cytosine
• B. Uracil, cytosine
• C. Guanine, uracil and cytosine
• D. Adenine, guanine

Answer 1

Answer: (B)

Uracil, cytosine

DNA and RNA both have four bases, that includes two purines and two pyrimidines, in the nucleotide chains. There are two purines namely adenine and guanine and three pyrimidines namely cytosine, thymine and uracil. The purines adenine and guanine and the pyrimidine cytosine are common to both DNA and RNA. DNA has the pyrimidine thymine; RNA has the pyrimidine uracil. Thus, the correct answer is option B.