Consider an experiment in which an Hfr strain of E. coli bacteria with the StrS, his+, met+ alleles in its genome is mixed with an F- strain of E. coli with the StrR, his-, and met- alleles in its genome. After the cells have been cultured together for 8 hours, the mixture of cells is plated on minimal media containing Streptomycin. Which genotype do you expect to be most common among the colonies that grow?F+: StrR, his+ and met+ Solution Answer D) F-: StrR, his+ and met+ Explanation - We know that Hfr strain is a high frequency recombination strain in which the F plasmid (fertility factor) is integrated in its genome/chromosomal DNA. this way, Hfr has ability to transfer the entire genome sequence to its recipient (F- strain), but it requires a long time of physical contact with the recipient due to which the recipient get some gene (long time physical contact is rarely achieved) and remains as F- strain. also, there is no back transfer of genes to the Hfr cells from the F- cells. hence, in this case, only F- strain will survive which has resistance against Streptomycin and able to synthesize its amino acids on minimal media. which is a recombinant F-: StrR, his+ and met+..