Chapter 12, Problem 17P

A $1-mL$ sample of the bacterium $\text{E}\text{.coli}$ 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 $\text{-}$ size samples are removed and plated on identical complete $\text{-}$ medium growth plates. Plate $\text{1}$ is immediately wrappedin a dark cloth, but plate $\text{2}$ is not covered. Both plates are left at room temperature for $\text{36}$ hours and then examined. Plate $\text{2}$ is seen to contain many more growing colonies than plate $\text{1}$. Thinking about DNA repair processes, how do you explain this observation?