The labels for ten bacterial strains were mixed up and now you do not know the i
ID: 271900 • Letter: T
Question
The labels for ten bacterial strains were mixed up and now you do not know the identity of each strain. You know all strains are auxotrophs and each one has a single, unique mutation. You set up pairwise crosses between bacterial strains and select for exconjugants by plating on MM. Use the information below to determine F-, F+, and Hfr strains. (- means no colonies grow on MM after conjugation, + means few colonies, +++ means many colonies) Please Explain why F- strains: A1, A2, B5 F+ strains: A3, A4, B3, B4 and Hfr strains: B1, B2, A5
A1
F- strains: ______________ F+ strains: _________________ Hfr strains:
A1
+++ +++ + + - A2 +++ +++ + + - A3 - - - - + A4 - - - - + A5 - - - - +++Explanation / Answer
F- strains: A1, A2, B5, F+ strains: A3, A4, B3, B4, Hfr strains: B1, B2, A5
F- x F-, F+ x F+, Hfr x Hfr, and Hfr x F+ all will give – (no conjugation, so no prototrophic exconjugants) F+ x F- will give + (low frequency transfer of genomic marker: few prototrophic exconjugants).
Hfr x F- will give +++ (higher frequency transfer genomic marker: more prototrophic exconjugants).
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