Question

4. Nutritional status, mutation, and expression of the lac operon. For each of the following conditions, indicate how much (a lot, a little, or none) of the lacZ gene (z-gene) product, beta- galactosidase, is being synthesized. NUTRITIONAL STATUS OF THE BACTERIA +lactose/-glucose +lactose/+glucose -lactose/+glucose genetic status normal (no mutation) mutation a mutation b mutationc important: these are nor the same mutations as the ones in your class handout mutation a: a mutation in the start codon for the lacA (A-gene) that converts it into a stop codon mutation b: a mutation in the repressor so that it cannot un-bind from the operator (meaning that the repressor is always bound to the operator under all conditions) mutation : a mutation in allolactose that prevents it from binding to the repressor protein

Answer 1

Genetic status	+lactose/-glucose	+lactose/+glucose	-lactose/+glucose
Normal	A lot	little	None
mutation a	A lot	little	None
mutation b	None	None	None
mutation c	None	None	None

In normal condition, when lactose is absent lac operon ( lactose inducible operon) will be switched off. In presence of lactose and absence of glucose , there will be positive regulation and more than basal level of beta-galactosidase will be synthesized. In presence of both lactose nad glucose, beta galactosidase synthesis will be equal to basal level because can be utilized directly.