The GATE Grind

GATE 2021 ES – Question 28

Environmental Microbiology · Cell Chemistry and Cell Biology · 1 mark · Multiple choice

Which nucleotide pairing is present in double-helical DNA?

  1. Thymine–cytosine
  2. Adenine–thymine
  3. Cytosine–adenine
  4. Uracil–thymine

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Show answer and explanation

Correct answer: (B) Adenine–thymine

Explanation

Canonical DNA base pairs are adenine–thymine and guanine–cytosine. Therefore **B** is the listed valid pair. Uracil normally replaces thymine in RNA, and the other pairs do not match the standard complementary DNA pattern.

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