Five Hfr strains A through E are derived from a single F+ strain of E

Five Hfr strains A through E are derived from a single F+ strain of E. coli. The following chart shows the entry times in minutes of the first five markers into an F- strain when each Hfr strain is used in an interrupted-conjugation experiment:

1. Draw a map of the F+ strain, indicating the positions of all the genes and their distances apart in minutes. Show the insertion point and orientation of the F plasmid in each Hfr strain on your map.

2. When using Hfr strain A, which gene would select to obtain the highest frequency of donor alleles in the Hfr exconjugants out of the following: xyl, mal, str, his?

A B ? D E malt 1 adet 13 pro 3 prot 10 hist 7 strs 11 hist 28 met+ 29 gal* 16 galt 17 sert 16 galt 38 xyl+ 32 hist 26 prot 23 adet 36 prot 44 malt 37 adet 41 mett 49 hist 51 mett 70 strs 47 ser+ 61 xylt 52 Useful formulae The distance between two markers for P1 transduction can be calculated using the formula: d = 2 + (1-11) Where d is the distance (in minutes) between two genes Or • (1-v7) d = 100 Where d is the distance (in kb) between two genes and f is the co-transduction frequency expressed as a fraction.