In RNA, Uracil forms 2 hydrogen bonds with adenine.

In RNA, Uracil forms 2 hydrogen bonds with adenine.

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

Answer: (B)

RNA base pairing is governed by specific hydrogen-bonding rules between complementary bases. In RNA, adenine pairs with uracil using two hydrogen bonds, which is the RNA counterpart to the DNA A–T pairing (where thymine, not uracil, is used). Cytosine pairs with guanine using three hydrogen bonds, not with adenine. Thymine pairs with adenine in DNA, not in RNA, since RNA uses uracil instead of thymine. So the statement that uracil forms two hydrogen bonds with adenine in RNA is the correct description of how these bases pair.

RNA base pairing is governed by specific hydrogen-bonding rules between complementary bases. In RNA, adenine pairs with uracil using two hydrogen bonds, which is the RNA counterpart to the DNA A–T pairing (where thymine, not uracil, is used). Cytosine pairs with guanine using three hydrogen bonds, not with adenine. Thymine pairs with adenine in DNA, not in RNA, since RNA uses uracil instead of thymine. So the statement that uracil forms two hydrogen bonds with adenine in RNA is the correct description of how these bases pair.