A conjugation experiment is performed in Escherichia coli us

A conjugation experiment is performed in Escherichia coli using the parents Hfr arg+ lys+ met+ his+ strS and F- arglys- met- his- strR. The mating was interrupted at several times and plated on several different media with the following results. The table below shows the number of colonies obtained on different media as indicated.

1. A conjugation experiment is performed in Escherichia coli using the parents Hfr arg lyst met his strs and F arg lys met his str. The mating was interrupted at several times and plated on several different media with the following results. The table below shows the number of colonies obtained on different media as indicated Minimal medium plus streptomycin plus Histidine Arginine Arginine Arginine Histidine Histidine Lysine Lysine Time (min.) Methionine Methionine Lysine Methionine 10 50 400 15 20 20 30 170 60 200 1000 600 350 550 1000 40 a) What is the order of the four auxotrophic genes with respect to the starting point of transfer (0) b) Conjugation is allowed to proceed for 60 min and lys str cells are selected. A total of 1000 lyst cells are tested further and the following genotypes are obtained his argt 600 his arg 400 a- 1,000 hist met+ 500 hist met 500 1,000 arg met 900 arg met 100 1,000 Calculate the map distances between met, arg, and his and define the exact order. Does this result resolve any uncertainties in your answer to part a, explain why?

Solution

a) The order of the genes will be :

Met - Arg - Lys - His

b) His+ arg+ = 600 his+arg^- = 400 =1000

his-+met+ = 500 his+ met- = 500 =1000

arg+ met+ = 900 arg+met- = 100 =1000

The order of the genes will be Met-His-Arg