What would be the effect on DNA replication of mutations that destroyed each of the following activities of DNA polymerase I?a. 3′→5′ exonuclease activityb. 5′→3′ exonuclease activityc. 5′→3′ polymerase activity

a. 3′→5′ exonuclease activity = No proof reading

b. 5′→3′ exonuclease activity = No primer removal

c. 5′→3′ polymerase activity = No gap filling

Explanation:

a) 3′→5′ exonuclease activity = No proof reading

3′→5′ exonuclease activity of DNA polymerase I is responsible for proof reading so that if a wrong nucleotide is inserted during replication, it could be removed. So if a mutation will occur in the domain which is responsible for 3′→5′ exonuclease activity error prone DNA replication will occur.

b. 5′→3′ exonuclease activity = No primer removal

5′→3′ exonuclease activity is useful in removing primers so that appropriate nucleotides could be inserted in the lagging strand. But if mutation will occur in this part of DNA polymerase I then primer will not be removed and replication of lagging strand will be at halt.

c. 5′→3′ polymerase activity = No gap filling

5′→3′ polymerase activity of DNA polymerase I, joins the nucleotides in the lagging strand where the gaps have been created after removal of primer. So the gaps created after removal of primer in the lagging strand will not be filled if there will be a mutation in this segment of DNA polymerase I.

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.