Biology help Following Esther and Joshua Lederberg\'s (1952) classic experiment,
ID: 148932 • Letter: B
Question
Biology help
Following Esther and Joshua Lederberg's (1952) classic experiment, you set up a bacterial culture from a small number of streptomycin-sensitive cells. You allow the cells to grow to high density and plate a few of them. You allow the colonies to grow until they are visible to the naked eye. The colonies are distributed as shown in Figure A below. You replica plate this plate onto two separate plates containing high concentrations of streptomycin. After a short incubation period, you observe 3 colonies on each plate. Assuming that streptomycin resistance arises through directed mutation (or acquired inherited resistance), how would you expect the resistant colonies to be distributed on the two plates? (Note: the dashed lines are only to guide you on the position of the colonies.) C) Like B (both plates) Like C (both plates) O Like D (both plates) One plate like B and one plate like C O One plate like B and one plate like DExplanation / Answer
The answer will be both plates like C.
The position of the colonies in B and D are same as the replica plate. If they were resistant colonies and present before exposure to streptomycin, then it can be said that the susceptible died after exposure and these resistant colonies survived and multiplied in their own area, but clustering in a different area as seen in C indicates that these are the newly appeared mutants under the influence of the antibiotic.
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