In RNA, which nitrogenous base forms complementary base-pairing hydrogen bonds with adenine?

• A. Uracil (U)
• B. Guanine (G)
• C. Thymine (T)
• D. Cytosine (C)

Answer: (A)

Verified step by step guidance

1. Recall that RNA is a nucleic acid composed of four nitrogenous bases: adenine (A), uracil (U), guanine (G), and cytosine (C).
2. Understand that in RNA, base pairing occurs through hydrogen bonds between complementary bases, similar to DNA but with a key difference.
3. Remember that in DNA, adenine pairs with thymine (T), but RNA does not contain thymine; instead, it contains uracil (U).
4. Therefore, in RNA, adenine (A) forms complementary base pairs with uracil (U) through hydrogen bonding.
5. Conclude that the nitrogenous base that pairs with adenine in RNA is uracil (U), not guanine, thymine, or cytosine.