Question

You have discovered an "Exo-" mutant form of DNA polymerase in which the 3′-to-5′ exonuclease function has been destroyed but the ability to join nucleotides together is unchanged. Which of the following properties do you expect the mutant polymerase to have?

(A) It will polymerize in both the 5′-to-3′ direction and the 3′-to-5′ direction.
(B) It will polymerize more slowly than the normal Exo+
polymerase.
(C) It will be more likely to generate mismatched base pairs.
(D) All of the above.
All of the above

Answer 1

The mutant DNA polymerase with a destroyed 3′-to-5′ exonuclease function is expected to polymerize in both directions, polymerize more slowly than the normal polymerase, and be more likely to generate mismatched base pairs.

Step-by-step explanation:

The mutant form of DNA polymerase you discovered with a destroyed 3′-to-5′ exonuclease function but unchanged nucleotide joining ability is expected to have the following properties:

1. It will polymerize in both the 5′-to-3′ direction and the 3′-to-5′ direction. Typically, DNA polymerases only extend in the 5′-to-3′ direction, but the loss of the exonuclease function allows the mutant polymerase to polymerize in the opposite direction as well.
2. It will polymerize more slowly than the normal Exo+ polymerase. The exonuclease function helps correct errors during replication, so the mutant polymerase without this function would be slower in fixing mistakes.
3. It will be more likely to generate mismatched base pairs. Without the exonuclease function, the mutant polymerase has a reduced ability to proofread and correct errors, leading to an increased likelihood of introducing mismatched base pairs.

Therefore, option (D) All of the above is the correct answer.