Question

Which of the following is not true of the three operators of the lac operon? question 2 options:

a. one of the operators is contained within the promoter region
b. one of the operators is contained within the lacz gene
c. two of the three operators are upstream of the transcriptional start site.
d. the dna between the operators bound by the lac repressor is looped out to sterically hinder rna polymerase
e. all three operators are bound simultaneously by the lac repressor to repress the expression of the operon.

Answer 1

The incorrect statement about the lac operon is that one of the operators is contained within the promoter region. The operators are named O1, O2, and O3, with O2 within the lacZ gene and O3 within the lacI gene, but none are within the promoter.

Step-by-step explanation:

The statement regarding the lac operon that is not true is: 'one of the operators is contained within the promoter region'. In the lac operon, there are three operators named O1, O2, and O3. O1 is located adjacent to the promoter, whereas O2 is situated within the lacZ gene, and O3 is located at the end of the lacI gene. The operators O2 and O3 being located within the actual genes were harder to detect and do not individually affect lactose-induced derepression of the lac operon. However, when both O2 and O3 are mutated together, the binding of the repressor to the operon is significantly decreased. Moreover, the DNA between the operators bound by the lac repressor is indeed looped out to sterically hinder RNA polymerase, and all three operators can be bound simultaneously by the lac repressor to repress the expression of the operon.