17. Mutation, Repair, and Recombination

Which of the following repair pathways uses a methylated strand of DNA to correct DNA damage?

Which of the following repair pathways repairs damage that causes distortions in the double helix?

True or False:Translesion DNA synthesis is the first mechanism the cell uses to repair DNA damage?

Which of the following pathways is an error-free way to repair double-stranded breaks?

Answer the following questions concerning the accuracy of DNA polymerase during replication.

Identify two mechanisms that can correct the kind of abnormality resulting from the circumstances identified in part (c).

Answer the following questions concerning the accuracy of DNA polymerase during replication.

If a DNA replication error is detected by DNA polymerase, how is it corrected?

Answer the following questions concerning the accuracy of DNA polymerase during replication.

DNA mismatch repair can accurately distinguish between the template strand and the newly replicated strand of a DNA duplex. What characteristic of DNA strands is used to make this distinction?

Answer the following questions concerning the accuracy of DNA polymerase during replication.

If the kind of abnormality identified in part (c) is not corrected before the next DNA replication cycle, what kind of mutation occurs?

Answer the following questions concerning the accuracy of DNA polymerase during replication.

If a replication error escapes detection and correction, what kind of abnormality is most likely to exist at the site of replication error?

Answer the following questions concerning the accuracy of DNA polymerase during replication.

What general mechanism do DNA polymerases use to check the accuracy of DNA replication and identify errors during replication?

A 1-mL sample of the bacterium E. coli is exposed to ultraviolet light. The sample is used to inoculate a 500-mL flask of complete medium that allows growth of all bacterial cells. The 500-mL culture is grown on the benchtop, and two equal-size samples are removed and plated on identical complete-medium growth plates. Plate 1 is immediately wrapped in a dark cloth, but plate 2 is not covered. Both plates are left at room temperature for 36 hours and then examined. Plate 2 is seen to contain many more growing colonies than plate 1. Thinking about DNA repair processes, how do you explain this observation?

A strain of E. coli is identified as having a null mutation of the RecA gene. What biological property do you expect to be absent in the mutant strain? What is the molecular basis for the missing property?