You have identified a mutant E. coli strain that cannot synthesize histidine (Hi

Question

You have identified a mutant E. coli strain that cannot synthesize histidine (His-).
To determine the location of the his- mutation on the E. coli chromosome, you perform interrupted mating experiments with 5 different Hfr strains. The following chart shows the time of entry (minutes, in parentheses) of the wild-type alleles of the first 5 markers (mutant genes) into the His- strain.

Hfr A -------- his (1) man (9) gal (28) lac (37) thr (45)
Hfr B -------- man(15) his (23) cys (38) ser (42) arg (49)
Hfr C -------- thr (3) lac (11) gal (20) man (39) his (47)
Hfr D -------- cys (3) his (18) man (26) gal (45) lac (54)
Hfr E -------- thr (6) rha (18) arg (36) ser (43) cys (47)

On the map below of the circular E. coli chromosome, indicate (1) the relative location of each gene relative to thr (located at 0/100 Min), (2) the position where the sex factor is integrated in each of the five Hfr’s, and (3) the direction of chromosome transfer for each Hfr (indicate direction with an arrow or arrowhead).

Explanation / Answer

You have identified a mutant E. coli strain that cannot synthesize histidine (Hi

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