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. Select all that apply. The promoter sequence is correct/functional. The repressor protein is produced. The operator sequence is correct/functional. Beta-galactosidase is produced from the lacZ gene. Permease is produced from the lacY gene.

Answer 1

Answer

The lac operon possesses two kinds of genes, which includes structural genes and regulatory gene. Structural genes are those that are transcribed into mRNA, and there are 3 types of structural genes namely lac Z, lac Y, and lac I. The regulatory genes are present in the lac operon: the operon and the promoter, which are not transcribed.

The structural gene

lac Z codes for protein beta-galactosidase.

lac Y codes for beta-galactosidase permease

lac A codes for beta-galactosidase transacetylase.

The repressor protein synthesized by gene "I" binds to the operator and inhibits the transcription. If the bacterium lacks lactose in its environment and then lactose is suddenly introduced then immediately high concentration of lactose in the cell binds to the repressor and makes it unavailable for binding and allows RNA polymerase to transcribe the structural genes.

A mutation in the "I" gene and operator gene (O) causes constitutive expression of the protein. The mutation in "O" gene modifies the structure of the operator gene. As a result, the repressor no longer binds to the operator, and RNA polymerase initiates transcription continuously. Similarly, if lac “I” is mutated, the repressor protein would not function properly, and the lac operon would be over expressed.

Based on the above provided data, each region of the lac operon on the F' plasmid, I+ P+ Oc Z− Y+ determines as following:

The promoter sequence is correct/functional.

The repressor protein is produced.

Permease is produced from the lac Y gene.