What are the correct genotypes for the following E, coil mutants with the follow

Question

What are the correct genotypes for the following E, coil mutants with the following phenotypes? An auxotroph for arginine and a prototroph for histidine Able to grow on xylose alone, but unable to grow on lactose alone Requires the vitamin biotin to grow, and able to digest glucose Sensitive to the antibiotic ampicillin and an auxotroph for tryptophan Can use glucose as a source of carbon, resistant to streptomycin, and requires thiamine the correct genotypes for the following I cdi mutants with the following for growth In a cotransduction experiment. DNA was isolated from a donor strain that was porA' and sirC' and sensible to tetracycline. A recipient strain is porA' and sirC' and is resistance to tetracycline After transductiontion. the E. colt cells were first plated on a medium containing prolirv streptomycin, and tetracycline. Colonies were then restreaked on a medium containing streptomycin, and tetracycline. Note both media types had carbon and nitrogen sources the E. coli could metabolize. The following results were obtained 70 colonics grew on the medium containing prolinc. streptomycin and tetracycline, but only 2 of the 70 colonies were able to grow when restreaked on medium containing streptomycin and tetracycline, hut lacking proline If we assume the average size of the DNA fragment is 2 minutes, how far apart are these two genes? What would you expect the cotransduction frequency to be if the average size of the DNA fragment was 4 minutes? How does the size of the cotransduction DNA fragment influence the cotransduction frequency/

Explanation / Answer

8. A) arg+, his+

B) xyl+, lac-

C) bio- , glu+

D) amp-, tryp+

E)glu+, str+, thia-

9. A) For distance the C.F. will be calculated first which will be: 2/70 i.e. .028

So the distance will be:   C.F.= {1- d/l }3

   d = 1.4

B) If the size of cotransduction DNA fragment is 4 min then the cotransduction frequency would be 0.27( From the above formula taking d=1.4 and l=4)

C) The size of cotransduction DNA fragment influences the cotransduction frequency. The relation between these factors are as follows:

C.F.= {1- d/l }3

Where C.F.= cotransduction frequency

d = Distance between two genes

l = ize of cotransduction DNA fragment

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