How does base pairing in RNA differ from base pairing in DNA?

• A. RNA uses uracil (U) instead of thymine (T), so adenine pairs with uracil (A–U) rather than adenine pairing with thymine (A–T).
• B. In RNA, guanine pairs with thymine (G–T) instead of pairing with cytosine (G–C).
• C. RNA uses thymine (T) instead of uracil (U), so adenine pairs with thymine (A–T) rather than adenine pairing with uracil (A–U).
• D. In RNA, cytosine pairs with adenine (C–A) instead of pairing with guanine (C–G).

Answer: (A)

Verified step by step guidance

1. Recall that DNA and RNA are both nucleic acids composed of nucleotide bases, but they differ in the specific bases they contain.
2. Identify the four bases in DNA: adenine (A), thymine (T), cytosine (C), and guanine (G). In RNA, thymine (T) is replaced by uracil (U), so the bases are adenine (A), uracil (U), cytosine (C), and guanine (G).
3. Understand the base pairing rules in DNA: adenine pairs with thymine (A–T) and cytosine pairs with guanine (C–G) through hydrogen bonds.
4. Recognize the base pairing rules in RNA: adenine pairs with uracil (A–U) instead of thymine, while cytosine still pairs with guanine (C–G).
5. Conclude that the key difference in base pairing between RNA and DNA is that RNA uses uracil (U) in place of thymine (T), so adenine pairs with uracil (A–U) in RNA, whereas in DNA adenine pairs with thymine (A–T).