1. This problem is an example of how conjugation can be used to map genes in bac

Question

1. This problem is an example of how conjugation can be used to map genes in bacteria. In this experiment, the Hfr strain used is a prototroph and contains genes to make methionine (met+), leucine (leu+), and uracil (ura+). Since it is Hfr, it contains the F factor This Hfr strain is sensitive to the antibiotic streptomycin (Sm2). The Hfr stain is mixed with an F- strain which is a triple auxotroph because it cannot make its own methionine (met-) leucine (leu-), and uracil (ura-). This F- strain has a gene Sm* which gives it streptomycin resistance. The Hfr and F-strain are allowed to mate and cultures are interrupted after 10 min, 20 min, and 30 min and then plated on CM+Sm media (see below) to select for the F- exconjugants. Colonies from each interrupted mating were then plated on the following media: CM-met, CM-met, leu, and CM-met, leu, ura (see below). Controls were also inoculated on various media. Complete the chart below and answer the questions MM minimal media CM-complete media CM +Sm complete media with streptomycin CM-met - complete media except for methionine (left out) CM - met, leu complete media except for methionine and leucine (left out) CM-met, leu, ura complete media except for methionine, leucine, and uracil (left out) a. Fill in each box with a + to indicate growth or-for no growth. Hfr F- (Before F- (10 min after F- (20 min F-(30 min after Conjugation) Conjugation) after Conjugation) Conjugation) CM CM + Sm CM met CM - met, leu CM - met, leu ura which cells will form colonies - Hfr, original F-, and/or the exconjugants? Will the exconjugants be F+ or F-? What is the order of the genes met, leu, and ura? Start with the gene which is closest to b. After mixing together the Hfr and F-strain and plating the mix of calls on CM+Sm, c. d. the "point of transfer" in the Hfr strain.

Explanation / Answer

B. the colonies formed will be of both Hfr and F- strain.

C. The exconjugants will be of F+ strain.

D. order of genes- Met-leu-ura.

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