1. In E. coli the following Hfr strains donate the markers shown below in the orders given:
Hfr strain Order of gene transfer
1 G E B D N A
2 P Y L G E B
3 X T J F P Y
4 B E G L Y P
All the Hfr strains were obtained from the same F+ strain. What is the gene order on the original bacterial chromosome?
2. An Hfr strain (arg+, bio+, leu+) is mated to an F- strain (arg-, bio-, leu-). Assume that this Hfr strain transfers arg+ last. You grow the exconjugants on arg- media, supplemented with leu+ and bio+. You recover 423 arg+ exconjugants. These are tested individually for bio and leu and you find the following distribution of genotypes:
arg+, bio+, leu+ 360
arg+, bio+, leu- 9
arg+, bio-, leu+ 0
arg+, bio-, leu- 54
Determine the gene order and the recombination distances between the three genes.