The general transducing phage P1 is grown on a wild type bacterial strain (cys +

Question

The general transducing phage P1 is grown on a wild type bacterial strain (cys+ pyr+ trp+). The resulting phage are mixed with an auxotrophic bacteria that require cysteine, pyrimidine, and tryptophan (cys- pyr- trp-). The auxotroph cannot synthesize these molecules due to the mutation; therefore the only way that they can survive is for you to supplement their diet with them. Recombinants are selected on medium containing pyrimidine and tryptophan. Results are shown below:

Spread on Plate                                                        Colonies arising on plate

Phage only (108)    0

Recipient cells only (108)                                                         4

Mixture of phage and cells (108 of each)                                  200

What is the source of the 4 colonies on the plate with recipient only?

Explanation / Answer

The general transducing phage P1 is grown on a wild type bacterial strain (cys+ pyr+ trp+). The resulting phage are mixed with an auxotrophic bacteria that require cysteine, pyrimidine, and tryptophan (cys- pyr- trp-). The auxotroph cannot synthesize these molecules due to the mutation; therefore the only way that they can survive is for you to supplement their diet with them. Recombinants are selected on medium containing pyrimidine and tryptophan. Results are shown below:

Spread on Plate Colonies arising on plate

Phage only (108) 0

Recipient cells only (108) 4

Mixture of phage and cells (108 of each) 200

What is the source of the 4 colonies on the plate with recipient only?

the selection of was------cys---- colonies

the source of the 4 colonies on the plate with recipient ---arose in the absence of phage -may due to SPONTANEOUS REVERTANTS

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.