While working in Dr. Strap’s lab you identify a number of E. coli mutants that o
ID: 218654 • Letter: W
Question
While working in Dr. Strap’s lab you identify a number of E. coli mutants that only grow in the presence of cysteine. Your supervisor suggests that the next step is for you to map the cys gene you have discovered relative to other known mutations. To do this, you start with bacterial strains:
Hfr cys- gal+ his+ lac+ pur+ trp+ tons
F- cys+ gal- his- lac- pur- trp- tonR
cys- his- pur- trp- = auxotrophic for cysteine, histidine, purines, tryptophan.
lac- gal- = cannot metabolize lactose or galactose.
tons = sensitive to phage T1.
If you supplement the minimal media with glucose, histidine, purines and T1 phage, what recombinant classes will you grow? Show your work.
Explanation / Answer
Hfr strain would grow as recombinant as it is positive for histidine, purine and T1 phage but negative for galactose . Now since the sugar source is directly glucose, it can be metabolised easily unlike galactose which requires enzyme for its metabolisation.
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