Question

2. You have performed the following mating experiment using Hfr and F"strains of Escherichia coli:(4 marks) Hfr (asp+ trp+ mal+ StrepS) x F (asp-trp-mal- Strep). Strep = streptomycin, an antibiotic Asp = aspartic acid, an amino acid Trp = tryptophan, an amino acid Mal = maltose, a sugar molecule, can be used by some organisms as an energy source rather than glucose (a) What selective media would you use to score recombinant colonies that have received all of the markers from the Hfr donor? (b) If you combine the two strains and plate them on a minimal media supplemented with maltose, which strains (F", Hfr, recombinants, or none) will grow? Briefly explain your answer. (c) During the conjugation of these two strains of E.coli, which strain receives the chromosome and which strain transfers the chromosome?

Answer 1

A) Minimal media without any supplement and supplied with streptomycin . It will allow us to score recombinant colonies that have all of the markers from the Hfr donor.

B) Hfr and recombinants will grow beacuse recombinant will be asp+ , trp+ , Mal+ , so can synhtesize these supplements on their own.

C) Hfr transfers the chromosome and F- will receive the chromosome .