Question

If an incorrect nucleotide is incorporated once per thousand nucleotides, proofreading normally catches 999 incorrectly incorporated nucleotides per thousand, and mismatch repair detects 999 residual replication errors per thousand, leading to a 1 per billion error rate for replication as a whole. What will be the overall error rate of replication in a strain of E. coli that has an intact mismatch repair pathway but has a mutation in DNA polymerase that results in it having no proofreading activity?

Answer 1

Huh? What do you mean

Answer 2

The incorporated nucleotide would have the overall rate of replication would be 1 in 1000000. That is 1 in 1 million

This repair mechanism works in three different levels.

Each of the three levels have their error rate to be 1 in 1000 nucleotides. Given three levels combined, we have an error rate that is 1 billion.

1000³ = 1 billion

This question tells us that the proof reading property is lost due to a mutation.

While assuming a error rate of 1 in 1000, we can get the overall error rate to be 1 per 1000 for the mismatched pair and also 1 in 1000 for the polymerase addition.

This would be 1000 x 1000

= 1000000

Therefore the overall rate of replication would be 1 in 1000000.

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