AP BIOLOGY

Detailed explanation-1: -Definition. Uracil (U) is one of the four nucleotide bases in RNA, with the other three being adenine (A), cytosine (C) and guanine (G). In RNA, uracil pairs with adenine. In a DNA molecule, the nucleotide thymine (T) is used in place of uracil.

Detailed explanation-2: -In DNA, adenine always pairs with thymine (A-T), and guanine always pairs with cytosine (G-C). RNA is the same, except that adenine always pairs with uracil (A-U).

Detailed explanation-3: -Uracil pairs with adenine through hydrogen bonding. When base pairing with adenine, uracil acts as both a hydrogen bond acceptor and a hydrogen bond donor. In RNA, uracil binds with a ribose sugar to form the ribonucleoside uridine. When a phosphate attaches to uridine, uridine 5′-monophosphate is produced.

Detailed explanation-4: -In DNA, adenine binds to thymine via two hydrogen bonds to assist in stabilizing the nucleic acid structures. In RNA, which is used for protein synthesis, adenine binds to uracil.

Detailed explanation-5: -In DNA/RNA base pairing, adenine (A) pairs with uracil (U), and cytosine (C) pairs with guanine (G).