Question

Which of the following lead(s) to a point mutation?

a. deamination of a cytosine base into a uracil base
b. benzo(a)pyrene conversion of guanine to a thymine base
c. deamination of 5-methyl cytosine into thymine
d. a and b
e. a,b, and c

Answer 1

Options a, b, and c all describe processes that can lead to a point mutation: deamination of cytosine to uracil, benzo(a)pyrene causing a conversion of guanine to thymine, and the deamination of 5-methyl cytosine to thymine. Therefore, the correct answer is e. a, b, and c.

Step-by-step explanation:

Regarding the question which of the following leads to a point mutation:

1. Deamination of a cytosine base into a uracil base
2. Benzo(a)pyrene conversion of guanine to a thymine base
3. Deamination of 5-methyl cytosine into thymine

Deamination is a process that involves the removal of amino groups from nucleotide bases, such as cytosine, which can lead to base pair substitutions, such as turning cytosine into uracil. Spontaneous deamination of cytosine converts it to uracil, and the replication process may then cause a guanine (G) to be mistakenly paired with adenine (A) instead of cytosine (C), leading to a G-C base pair being replaced by an A-T pair. Additionally, the deamination of 5-methyl cytosine into thymine also results in a point mutation. Chemical factors such as benzo(a)pyrene can cause structural changes to DNA bases, such as the conversion of guanine to thymine, leading to mutations upon DNA replication. Therefore, all the listed options can lead to point mutations, making the correct answer e. a, b, and c.