Biomolecules Question 54

54. RNA does not possess

(a) Uracil

(c) Adenine

(b) Thymine

(d) Cytosine

Show Answer

Answer : b

Hints & Solutions

(b) In RNA, pyrimidine thymine is replaced by uracil. Uracil is energetically less expensive to produce than thymine, which may account for its use in RNA. In DNA, however, uracil is readily produced by chemical degradation of cytosine, so having thymine as the normal base makes detection and repair of such incipient mutations more efficient.