AP BIOLOGY

Detailed explanation-1: -5-bromouracil (5BU) is a pyrimidine analogue of thymine which tautomerizes more readily than thymine does; the enol form of 5-bromouracil pairs with guanine and thereby causes the transition .

Detailed explanation-2: -5-Bromouracil (BrU) is a base analogue of thymine (T) which can be incorporated into DNA. It is a well-known mutagen, causing transition mutations by mispairing with guanine (G) rather than pairing with adenine (A) during replication.

Detailed explanation-3: -5-bromouracil replace thymine with cytosine thereby, causes the transition mutation. Thus, the correct answer is option B.

Detailed explanation-4: -5-Bromouracil (5-BrU, 5BrUra, or br5Ura) is a brominated derivative of uracil that acts as an antimetabolite or base analog, substituting for thymine in DNA, and can induce DNA mutation in the same way as 2-aminopurine.

Detailed explanation-5: -5-Bromouracil is used to treat neoplasms in the form of its nucleoside, 5-bromo-2-deoxy-uridine. 6-Mercaptopurine is an analogue of hypoxanthine and inhibits purine nucleotide synthesis and metabolism. 6-Mercaptopurine is used to treat acute leukemia.