LAC OPERON

In the lac operon the inducer is

• Allolactose

• Glucose

• Galactose

• All of the above

The lac operon is an example of an inducible operon. Which of the following describes the process that occurs when lactose is present?

• The lactose binds to the repressor, which inactivates it, and the repressor releases from the operator to turn translation on.

• The lactose binds to the repressor, which activates it, and the repressor binds to the operator to turn translation on.

• The lactose binds to the repressor, which inactivates it, and the repressor releases from the operator to turn translation on.

• The lactose binds to the repressor, which activates it, and the repressor binds to the operator to turn translation on.

A protein that binds to the operator and blocks the RNA polymerase

• Regulator

• Repressor

• Activator

• Corepresser

Operons are found in which of the following organisms?

• Bacteria (prokaryotes)

• Plants and animals (eukaryotes)

• Only animals

• Viruses

An operon consists of all the following EXCEPT

• Operator

• Promoter

• Regulatory gene

• Genes of the operon

What is the role of operons in prokaryotic gene expression?

• It makes the genes prokaryotic be turned on.

• It accounts for the regulation of gene activity in response to the needs of the cells.

• To make DNA for the gene.

• To make the gene turn off and on.

If the repressor is bound to the operator....

• RNA polymerase is able to bind; the operon is off.

• RNA polymerase is able to bind; the operon is on.

• RNA polymerase is unable to bind; the operon is off.

• RNA polymerase is unable to bind; the operon is on.

Where does the repressor in an operon bind?

• Operator

• Promoter

• Regulatory sequence

• TATA box

β-galactosidase → hydrolyze/ breakdown of lactose into glucose and galactose

• True
• False

During the absence of lactose, the lac operon is switched on.

• True

• False