Question

E. coli cells were spread on two agar plates [one containing only agar (plate 1) and the second containing streptomycin (plate 2) which kills all cells except those that are resistant mutants]. Both plates were allowed to grow for several generations. Cells were collected from the agar plate WITHOUT streptomycin and spread again on a fresh agar plate containing streptomycin (plate 3). More mutants were observed on plate 3 than were observed on plate 2. The experiment demonstrates

	A.	how to screen for environmental mutagens
	B.	that mutation occurs in prokaryotes as well as in eukaryotes
	C.	that in some cases mutations are caused by the selective agent itself
	D.	that mutations occur in the absence of the selective agent
	E.	a direct correlation between the amount of the selective agent used and the number of resistant mutants (one-hit relationship)

Answer 1

B. that mutation occurs in prokaryotes as well as in eukaryotes

D. that mutations occur in the absence of the selective agent

(both the options are correct but if only one is needed then more preferable will be option B. )