Which of the following nucleotides are examples of pyrimidines?
A. Cytosine
B. Adenine
C. Uracil
D. Thymine
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A, C and D only
Nitrogenous bases are of two types. Purines are adenine and guanine. Pyrimidines are cytosine, uracil and thymine.
A. Cytosine — Correct. It is a pyrimidine. It is present in both DNA and RNA.
B. Adenine — Incorrect. Adenine is a purine, like guanine.
C. Uracil — Correct. It is a pyrimidine. It is found in RNA, in place of thymine.
D. Thymine — Correct. It is a pyrimidine. It is found in DNA.
Note: It seems that there is a mistake in the original NTA paper, which prints ‘nucleotides’ when it should read ‘nitrogenous bases’. Cytosine, adenine, uracil and thymine are bases. A nucleotide is a base joined to a pentose sugar and a phosphate group.
NCERT Extract:
Structure of Polynucleotide Chain – …
