Which nitrogenous base is present in ribonucleic acid (RNA) molecules but absent in genomic DNA?
Answer and explanation
Correct answer: C. Uracil
- Step 1: Compare the nucleotide bases of DNA and RNA.
- Step 2: DNA contains adenine, guanine, cytosine, and thymine. RNA replaces thymine with uracil, which pairs with adenine via two hydrogen bonds.
Answer
Uracil.
Why not the others: Thymine is found in DNA, not RNA; cytosine and guanine are present in both DNA and RNA.
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