Question

QUESTION 36

You have added a drug that reduces DNA Ligase activity. What will happen to the rate at which Okazaki fragments are synthesized on the lagging strand? Explain your reasoning.

Answer 1

The only function of DNA ligse is joining of Okazaki fragments by the formation of an ester linkage with the 5'phosphate of the previous Okazaki fragment with the 3'OH of the next Okazaki fragment. This process occurs after the removal of the RNA primer by nick-translation in bacteria or by the activity of Fen 1 in eukaryotes. Therefore a reduction in ligase actvity may not affect the kinetics of the synthesis of Okazaki fragments. The joining of Okzaki fragments occurs after the polymerase has left the region where the fragments are awaiting the joining process. But reduction in ligase activity may result in occurrence of single strands breaks.