5. (6 Points) Benzer\'s Experiments A. Mutations rII1 and rI12 are known to fall

Question

5. (6 Points) Benzer's Experiments A. Mutations rII1 and rI12 are known to fall into the rILA and rITB cistrons (genes) respectively. Cells of E. coli B are infected simultaneously with phage strains rII1 and rI12 at a high moi. The progeny phage are collected and used to infect cells of E. coli K. This infection is also carried out at a high m.o.i., and the resulting phage are collected. These progeny are diluted and plated on both E. coli B and E. coli K. Do you expect more plaques on strain B, on strain K, an equal amount on both or is it impossible to tell? (circle one) E. coli K Equal on both E. coli B Can't tell B. rI13 and rII4 are two non-overlapping deletion mutations of rIIB cistron (gene). Mutations rII3 and rII4 are used to infect E. coli B at high m.o.i and the progeny phage collected. These phage are then used to infect strain K at very low multiplicity of infection (m.o.i.). The resulting phage are diluted and plated on both E. coli B and E. coli K. Do you expect more plaques on strain B on Strain K, an equal amount on both or is it impossible to tell? (circle one) Can't tell E. coli B E. coli K Equal on both

Explanation / Answer

A. Since the initial infection are done on B - strain, from the same type of phages as cistrons. So the same data or infection mode will be carried further or progenies even on K- strains , they are mutant ones which cannot further divide in K strain.In general, E.coli B strain supports the all types of phages whereas K strain only helps in the growth of wild types.

B. IN this the multiplicity of infectio used are different from each other, in deletion mutation if this is the condition there is a chance of reverting back of wild strain which can be grown on K strain plates. Thus you can obtain equla amont of growth on both plates since the resulting phage will be in a mixture of both wild type and mutated type.

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