A mutation occurs in a bacterium. Because of this mutation, DNA synthesis occurs

Question

A mutation occurs in a bacterium. Because of this mutation, DNA synthesis occurs at a very low rate. Upon analysis, it is found to have normal levels of activity of DNA polymerase I and III, DNA gyrase, and ligase. It also makes normal amounts of the wildtype dnaA, dnaB, dnaC, and SSB proteins. The sequence of the OriC (the origin of replication) of its chromosome is found to be normal (wildtype). What defect might account for the abnormally low rate of replication in this mutant? EXPLAIN.

5 pts: Submit a group response

5 pts: Name one correct possible defect

5 pts: Explain how the defect impacts replication

Explanation / Answer

Replication rate is high due to multiple polymerases can come into play and synthesize two daughter strands at the same time by using template strand of the parental DNA. One of these strands is the leading strand, while the other is the lagging strand. DNA polymerase III holoenzyme (HE) role in dna replication, necessary DNA polymerases, of E. coli consists of four (Pols I, II, IV, and V). Genetic analysis of mutation rates disclosed that (i) Pol II play an essential role in back-up proofreader for Pol III, (ii) Pols IV and V do not contribute much in replication fidelity, but can easily do so under elevated conditions, (iii) Pols IV and V, engage in opposite to that of Pol II, is distinct to the lagging strand, and (iv) Pol I also contribute inspecific fidelity of lagging-strand, restricted to the gap filling of the Okazaki fragment. Hence, it might be possible that defect in any one of the polymerase 3 holoenzyme result in the low rate of repliction

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