Recombination in bacteria
A particular Hfr strain normally transmits the pro+ marker as the last one during conjugation. In a cross of this strain with an F- strain, some pro+ recombinants are recovered early in the mating process. When these pro+ cells are mixed with F- cells, the majority of the latter are converted to pro+ cells that also carry the F factor. This job furthger explains these results.
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Solution Summary
Recombination in bacteria is featured. The mating processes and pro+ markers are examined.
Recombination in bacteria and in viruses that infect bacteria.
Four E. coli strains of genotype a+ b- are labeled 1,2,3 and 4. Four strains of genotype a- b+ are labeled 5,6,7, and 8. The two genotypes are mixed in all possible combinations and (after incubation) plated to determine the frequency of a+ b+ recombinants. The following results were obtained, where M = many recombinants, L = low numbers of recombinants, and O = no recombinants.
-----1----2----3---4
----------------------
5--O-M--M--O
6--O---M--M--O
7--L----O--O--M
8--O---L-L---O
On the basis of these results, assign a sex type (either Hfr, F+, or F-) to each of the strains.
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