In RNA, which base replaces thymine?

In RNA, which base replaces thymine?

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

Answer: (A)

RNA uses uracil in place of thymine. This substitution helps distinguish RNA from DNA and suits RNA’s typically shorter, single-stranded roles. Uracil pairs with adenine through hydrogen bonding just as thymine does with adenine in DNA, so the A–U pairing supports RNA structure and base-pairing during transcription. The main difference is that uracil lacks the methyl group found on thymine, making it cheaper to synthesize and appropriate for RNA biology. Thus, the base that replaces thymine in RNA is uracil.

RNA uses uracil in place of thymine. This substitution helps distinguish RNA from DNA and suits RNA’s typically shorter, single-stranded roles. Uracil pairs with adenine through hydrogen bonding just as thymine does with adenine in DNA, so the A–U pairing supports RNA structure and base-pairing during transcription. The main difference is that uracil lacks the methyl group found on thymine, making it cheaper to synthesize and appropriate for RNA biology. Thus, the base that replaces thymine in RNA is uracil.