Question

Which of the following statements about regulation of the lac operon is true? (Select all that apply)

Group of answer choices

A. When glucose is present, gene expression is activated by lactose.

B. The amount of glucose in the growth medium does not affect the level of gene expression activated by lactose.

C. The binding of the Lac repressor to the operator is not affected by the presence of glucose.

D. Gene expression is high when the Lac repressor is not bound to the operator and glucose is available.

E. In merediploid analysis of E. coli mutants, wild type lac O could not rescue a mutation in lac O

F. When the helix-turn-helix motif in the lac repressor binds inverted repeat sequences in the operator, DNA looping prevents RNA polymerase from binding the promoter sequence.

G. cAMP is an effector for CRP, which is a negative feedback loop regulator of lacZ

Answer 1

C,E & F

Explanation: Why others are wrong

a) When glucose is present, lac operon is off.

b) When glucose is present , lac operon is off. The glucose levels affect the transcription of lac operon

d) Gene expression is high when when repressor is not bound to operator & glucose is not available

g) CRP actually helps RNA polymerase to bind tightly to promoter and increases expression of lacz.