Question

Which of the following best describes the role of lactose in the lac operon?

Answer 1

Which of the following best describes the role of lactose in the Lac operon

Select one:
a. Lactose binds to the Lac operon promoter preventing RNA polymerase to express the Lac genes
b. Lactose is produced when the lac operon is activated
c. Lactose inhibits Beta galactosidase which breaks down Lactose
d. Lactose represses the expression of the lac genes when too much lactose is available
e. Lactose binds to Lac I, the inhibitor of lac gene expression

Answer 2

e. is the answer...lac genes contain the following:
1.lacZ encodes β-galactosidase
2.lacY encodes β-galactoside permease
3.lacA encodes β-galactoside transacetylase.
and it also contains operators and promoters...usually in absence of lactose the repressor binds to operator and prevents the transcription process..But when lactose is present the allolactose binds to the repressor thereby changing its conformation and decreasing its activity and finally the transcription occurs and the enzymes for the lactose metabolism are effectively produced.