Question

From the Luria-Delbruck fluctuation test, when would mutations arise in yeast cells to allow for survival in the presence of toxic levels of hydrogen peroxide?

a) Mutations are adaptive and would have appeared immediately in response to the hydrogen peroxide.

b) Mutations are random and would have appeared prior to being exposed to hydrogen peroxide.

c) Mutations are adaptive and would have appeared after most of the cells died in the presence of hydrogen peroxide.

d) Mutations are adaptive and would have formed prior to being exposed to hydrogen peroxide.

e) Mutations are random but would not have formed until after the hydrogen peroxide was introduced.

Answer 1

B) Mutations are random and would have appeared prior to being exposed to hydrogen peroxide.

The fluctuation test shows that mutations occur randomly in a growing culture, and are not induced by the selection agent. The fluctuation test shows that mutations occur randomly in a growing culture, and are not induced by the selection agent. If mutations were induced, for example by H2O2 on the plates, all the plates would have approximately the same number of colonies. In contrast, if mutations occured randomly in the growing population, when the culture was subdivided some tubes contained a population of cells in which the mutation occurred early in the growth period, whereas in others it may have occurred late, or not at all.