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. all of the above

Answer 1

All the listed options, including deamination of a cytosine base into a uracil base, benzo(a)pyrene conversion of guanine to a thymine base, and deamination of 5-methyl cytosine into thymine, lead to point mutations.

Step-by-step explanation:

The following leads to a point mutation:

• Deamination of a cytosine base into a uracil base, which upon replication can lead to a GC→AT transition mutation.
• Conversion of a base caused by chemicals like benzo(a)pyrene, which can alter the structure of guanine, potentially resulting in incorrect base pairing during DNA replication.
• Deamination of 5-methyl cytosine into thymine, leading to a point mutation if it is not repaired. This can convert a GC pair into an AT pair.

Therefore, all the listed options (deamination of a cytosine base into a uracil base, benzo(a)pyrene conversion of guanine to a thymine base, and deamination of 5-methyl cytosine into thymine) lead to point mutations.