Question

DNA mismatch repair enzymes preferentially repair bases on the newly synthesized DNA strand, using the old DNA strand as the template. If mismatches were simply repaired without regard for which strand served as template, would this reduce replication errors? Explain your answer (5 pts) Describe DNA replication (remember to mention all the enzymes involved) (10 pts)

Answer 1

It would not reduce replication errors. DNA polymerase uses the template strand to determine if the newly synthesized strand is free of errors or not, if an incorrect base pair is introduced, which is not complementart to the template strand, it uses its proofreadinf activity to rectify the error.

If this proofreading activity occured in a manner that either of the two strands were considered as templates, there would be no extreme variability in the new DNA synthesized. The parent DNA serves as a template because it sonsists of all the necessary information for the cells to function. If this is disregarded, and the new strand is considered as the template, if anything, it may lead to introduction of new errors by doubling its frequency through the genome.

The DNA proofreading system is extremely efficient, with a very low error rate. The template strand must always be referred to check for errors in the new strand for - 1)  Retention of the information from parent DNA, 2) To avoid errors and thus mutations, 3) To avoid an excessively random DNA which may or may not be properly functional