Question

For each region of the lac operon on the F' plasmid, I+ P+ Oc Z− Y+ , determine whether the region is wild type (that is, it produces a functional protein or it's a correct protein binding sequence) or whether the region is mutated. Select all that apply :
(A) The promoter sequence is correct/functional.
(B) The repressor protein is produced.
(C) The operator sequence is correct/functional.
(D) Beta-galactosidase is produced from the lacZ gene.
(E) Permease is produced from the lacY gene.

Answer 1

Answer:

A,B and E

Explanation:

• I+: I refers to the lac repressor, the + indicates that the repressor is functional

• P+:  P refers to the promoter region and the + indicates that the promoter is functional

• Oc:  O refers to the operator region, but the Oc indicates that the operator is constitutive ie. that it is always on/ can't be turned off.

• Z-: Z refers to the LacZ gene which produces β-galactosidase. Z- indicates that this gene is non-functional

• Y+:  Y refers to the LacY gene which produces the permease protein. Y+ indicates that this gene is functional

So based on the breakdown above:

• A is true because P+.

• B is true because I+.

• C is not true because the lac operon is an inducible system. The operator needs to be able to be repressed. In this case the operator is constitutive (always on)  which is not the correct form.

• D is not true because Z-, no β-galactosidase is produced.

• E is true because Y+.

Only A, B and E apply.