Six strains of E. coli (mutants 1-6) were isolated that had one of the following

Question

Six strains of E. coli (mutants 1-6) were isolated that had one of the following mutations affecting the lac operon. deletion of lacy lacOc mutation a missense mutation in lacZ inversion of the lac operon (but not an inversion of the lad gene) superrepressor mutation inversion of lacZ, Y and A, but not lad, P. 0 Part A Which of these mutations would prevent the strain from utilizing lactose? Enter the letters for your answer in alphabetical order with no spaces in between the letters. All pairwise partial diploids (merodiploids) were generated with the 6 E. coli strains. For each combination the plasmid included the entire lac operon, including the lad gene and its promoter. In this partial diploid analysis, mutant 1 was found to carry a deletion of lacY. Which of the other types of mutations would be expected to complement mutant 1 in these partial diploids, such that they would grow on medium that contained lactose as the sole carbon source? Enter the letters for your answer in alphabetical order with no spaces in between the letters.

Explanation / Answer

Part A

deletion of lac Y, inversion of lac operon

Lac Y gene codes for permease which helps the lactose to enter the cell

By the inversion of lac operon the promoter also gets reversed hence no transcription

Part B

Silent mutation(no change in the aminoacid)

Supressor mutation(another mutation in another region produces the wild type phenotype)

Mutation in one of the strand but wild type allele in the other strand

One mutant operator and one wild type operator will complement each other

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