Chemical Constituents of Cells · NCERT Biology

Which of the following nitrogenous bases is found exclusively in RNA and not in DNA?

  1. Adenine
  2. Guanine
  3. Uracil (RNA only)
  4. Thymine
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Correct answer: Uracil (RNA only)

Uracil is found exclusively in RNA, replacing thymine found in DNA. Unlike thymine, uracil lacks a methyl group at position 5. Adenine, guanine, and cytosine are present in both DNA and RNA.

Difficulty: Medium Question 8 of 20

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