How does base pairing differ between RNA and DNA?

• A. In RNA, adenine pairs with uracil (A–U), whereas in DNA, adenine pairs with thymine (A–T); guanine pairs with cytosine (G–C) in both.
• B. RNA uses A–T and G–C base pairs like DNA, but RNA additionally has thymine instead of uracil.
• C. In RNA, guanine pairs with uracil (G–U) as the standard Watson–Crick pair, whereas in DNA, guanine pairs with cytosine (G–C).
• D. In RNA, adenine pairs with cytosine (A–C), whereas in DNA, adenine pairs with thymine (A–T).

Answer: (A)

Verified step by step guidance

1. Recall the basic structure of DNA and RNA: both are nucleic acids composed of nucleotide bases, but they differ in one of the bases and in their sugar components.
2. Identify the four bases in DNA: adenine (A), thymine (T), guanine (G), and cytosine (C). In DNA, base pairing follows the rule that adenine pairs with thymine (A–T) and guanine pairs with cytosine (G–C).
3. Identify the four bases in RNA: adenine (A), uracil (U), guanine (G), and cytosine (C). Note that RNA contains uracil instead of thymine.
4. Understand the base pairing in RNA: adenine pairs with uracil (A–U), and guanine pairs with cytosine (G–C), similar to DNA except for the substitution of uracil for thymine.
5. Conclude that the key difference in base pairing between RNA and DNA is that RNA uses uracil (U) instead of thymine (T) to pair with adenine, while guanine and cytosine pair the same way in both molecules.