Which nitrogenous base is present in RNA but absent in DNA?
Answer and explanation
Correct answer: A. Uracil
- Step 1: Nucleic acids contain purines (adenine, guanine) and pyrimidines (cytosine, thymine, uracil).
- Step 2: DNA uses thymine (T), whereas RNA replaces thymine with uracil (U), pairing with adenine.
Answer
Uracil.
Why not the others: 'Thymine' is found in DNA, not RNA; 'Cytosine' is present in both DNA and RNA; 'Adenine' is present in both DNA and RNA.
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