Question

Pyrimidine base that has conferred additional stability to
DNA over RNA is

• A. Guanine
• B. Thymine
• C. Adenine
• D. Cytosine

Answer 1

The correct option is B Thymine

Part 1: Adenine
Adenine is a purine and not a pyrimidine. It is present in both DNA and RNA.

Part 2: Cytosine
Cytosine is a pyrimidine that is present in both DNA and RNA and hence cannot confer additional stability to just DNA and not RNA.

Part 3: Guanine
Guanine is a purine and not a pyrimidine. It is present in both DNA and RNA.

Part 4: Thymine
● Thymine or 5-methyl uracil is a pyrimidine that is present in DNA but not in RNA. In RNA, thymine is replaced by uracil which pairs with adenine.
● Thymine is less susceptible to mutations, compared to uracil and hence confers additional stability to the structure of DNA.
● Uracil is easily mutated, making the structure of RNA unstable.

Final answer
(d) Thymine