Molecular Biology of the Gene 7th Edition by Richard Losick, James Watson, Michael Levine, Tamara Baker, Alexander Gann

Exercise 14

You want to test two strains of E. coli for sensitivity to the DNA damaging agent, MMS (methyl methanesulfonate), an alkylating agent that methylates specific bases in DNA. After treating cells with a range of doses of MMS (by incubating the cells with MMS in liquid culture for various times), you plate the cells on a solid media to count survivors (given below). Plot the data for the two strains (percent survival vs. time of MMS exposure). Which strain is more sensitive to MMS? (Note that to count single colonies, you would have to serial-dilute the culture. For this example, we will ignore the serial dilution step.)