Question

1.

Which of the following organisms would produce functional lac products in the presence of IPTG?
A. I^s O^c Z^- Y⁺ A⁺
B. I^s O^c Z^- Y^- A^-
C. I⁺ O⁺ Z⁺ Y⁺ A⁺
D. I^-O^c Z⁺ Y⁺ A⁺
E. Both I^s O^c Z^- Y⁺ A⁺ and I^s O^c Z^- Y⁺ A⁺ are correct

2.

Which of the following statements is true about a lac operon with this genotype?
I^-d O⁺ Z⁺ Y^- A^-
A. The operon is repressible.
B. The operon is nonrepressible.
C. The mutation is cis-dominant.
D. The operon is uninducible.
E. None of the choices is correct.

3.

In an in vitro transcription assay to detect the level of transcription from a lac operon, one of the RNA precursors was tagged with a fluorescent label on the -phosphate. Which of the following is a likely outcome if transcription occurred?
A. The level of fluorescence would increase along the new RNA strand.
B. Each RNA would have a fluorescent tag on every other nucleotide.
C. The level of fluorescence would be very high in the assay buffer.
D. No fluorescence would be detected in the buffer at the end of the assay.
E. All of the choices are possible.

4.

Which of the following is an example of an allosteric interaction?
A. allolactose binding to a repressor
B. an aptamer binding to a riboswitch
C. polymerase binding to the promoter
D. repressor binding to the operator
E. both A. allolactose binding to a repressor and B. an aptamer binding to a riboswitch

5.

Which of the following would be effective in blocking transcription from the lac operon in the presence of permease?
A. antibody to RNA polymerase
B. antibody to the repressor protein
C. mutation in the operator
D. an antibody to -galactosidase
E. both antibody to RNA polymerase and mutation in the operator

Answer 1

Answer

Q1

D is correct choice.

Here Inhibitor is - that is not present.

Operator is c that is constitutive. And Z and Y are present.

Q2

B is correct choice

as Inhibitor is not present operon is nonrepressible.

Q4

e) both are correct

Q5

a) antibody to RNA polymerase

As RNA polymerase is inhibited transcription will not happen.

mutation of operator is Oc or making operator constitutive, that is it will always allow to proceed in lac operon.