In E.coli, four streptomycin-sensitive, prototrophic Hfr strains were mated with a stretomycin-resistant F^- strain auxotrophic for a number of nutritonal requirements. Matings were interrupted at various intervals, and cells were plated on streptomycin-containing minimal meduim supplemented with particular nutrients to test for gene transfer. Entry time (in minutes) of the first five genes for the four strains were as follows:
Hfr strain 1 : M+ (4), Z+(6), X+(11), W+(15),C+(17.5)
Hfr strain 2 : L+ (1), A+ (2), N+(5), C+ (6.5), W+(9)
Hfr strain 3 : A+(2.5), L+(3.5), B+(6), R+(11.5), U+ (15)
Hfr strain4 : Z+ (3), M+(5), U+ (11), R+(14.5), B+(20)
draw the map of the E.coli genome consistent with the data. Include distances between the genes and indicate the insertion points of the F plasmid in each Hfr strain.