In a classical genetic experiment,Newcombe spread E.coli cells on complete medium.After several generations of growth,he replica-plated the colonies onto two plates with complete medium plus a selective agent.Colonies on the first replica were left untouched,while on the second replica,they were respread,allowing bacteria from each colony to be "moved" to a new location on the plate.Significantly more mutants after spreading (resistant to the selective agent)were observed than if they had not been respread.The experiment was used to:
A)demonstrate how to screen for environmental mutagens.
B)demonstrate that in some cases mutations are caused by the selective agent itself.
C)provide evidence that mutations occur in the absence of the selective agent.
D)provide evidence that mutation occurs in prokaryotes as well as in eukaryotes.
E)show a direct correlation between the amount of the selective agent used and the number of resistant mutants.

Question

Quizplus · Accepted Answer

The experiment demonstrates that mutations occur independently of the selective agent, as the increase in mutants after respreading indicates that mutations had occurred prior to exposure to the selective agent, not as a result of it.

In a Classical Genetic Experiment,Newcombe Spread E