1)A mutant E. coli was constructed containing a nonpolar null mutation in the lacZ gene. The...

1)A mutant E. coli was constructed containing a nonpolar null mutation in the lacZ gene. The null mutation resulted in a nonfunctional LacZ product. In the presence of lactose, would this mutant E. coli be induced to make Lac permease (LacY)? Why or why not?

2)What is the difference between a repressor and aporepressor?

Solutions

Expert Solution

1.Ans. No, this mutant will not be induced to make Lac permease (LacY). LacZ is the gene which produces beta-galactosidase enzyme. Beta-galactosidase enzyme is responsible for breaking down of lactose into its monomers i.e. glucose and galactose. Glucose is the prefferred source of energy for E.coli. Hence, when glucose is not available, lactose available in the medium is taken in to use as source of energy by breaking down into glucose and galactose. Lac permease (LacZ) is the enzyme responsible for taking of lactose inside the E.coli cell. If an mutant E.coli produces nonfunctional LacZ product, then this mutant will not be able to break down lactose. Hence, there is no need for the E.coli to produce Lac permease enzyme. Hence, this mutant E.coli will not be induced to make Lac permease enzyme.

2.Ans. Repressor is the functional protein molecule upon binding of which at the operator inhibits the expression of structural genes (LacZ, LacY and LacA genes).

Aporepressor is inactive repressor which binds to a corepressor and binding of a corepressor to a repressor leads to binding of the repressor to bind the operator tightly.

gladiator answered 1 month ago

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