Contrast the various types of DNA repair mechanisms known to counteract the effects of UV radiation. What is the role of visible light in repairing UV-induced mutations?

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 the 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-sized 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?

It has been shown that infectious agents such as viruses often exert a dramatic effect on their host cell's genome architecture. In many cases, viruses induce methylation of host DNA sequences in order to enhance their infectivity. What specific host gene functions would you consider as strong candidates for such methylation by infecting viruses?

You have identified five genes in S. cerevisiae that are induced when the yeast are grown in a high-salt (NaCl) medium. To study the potential roles of these genes in acclimation to growth in high-salt conditions, you wish to examine the phenotypes of loss- and gain-of-function alleles of each. How would your answer differ if you were working with tomato plants instead of yeast?