Correct!

How many lac Z genes were present in the cells described in problem 5 that were able to grow on minimal media?

A.	Only 1, the lac Z allele on the bacterial chromosome.
B.	Only 1, the lac Z allele on the bacterial chromosome.
C.	Two, the lac Z allele on the bacterial chromosome and the lac Z allele on the bacterial chromosome.
D.	Two, the lac Z allele on the bacterial chromosome and the lac Z allele on the F' episome. E. coli cells with an F' episome may have more than one allele of a particular gene. In this case the lac Z allele of the F' episome is dominant to the lac Z allele of the bacterial chromosome. When cells are partially diploid for one or a few genes, dominance among the various alleles can be experimentally studied.
E.	Only 1, the lac Z allele on the F' episome.