Indicate the level of activity of the lac operon under the medium conditions listed below:

a) No lactose present, no glucose present

b) Lactose present, no glucose present

c) No lactose present, glucose present

d) Lactose present, glucose present

The lac operon is an operon required for the uptake and metabolism of lactose in bacteria. The carbon primary source for bacteria is glucose but when not available other sources of carbon can be use up such lactose.

Bacteria express the lac operon genes, which encode key enzymes for lactose metabolism. The lac operon is turn on when lactose is available, and glucose is not available.

Answers:

A. No lactose and no glucose present - lac operon is not activated

B. Lactose present and no glucose present - lac operon is activated

C. No lactose present and Glucose present - lac operon is not activated

D. Lactose present and Glucose present - lac operon is not activated.

a) No lactose present, no glucose. The lac operon is inactive.

b) Lactose present, no glucose present. The lac operon is active

c) No lactose present, glucose present. The lac operon is inactive

d) Lactose present, glucose present. The lac operon is inactive.

Explanation:

The lac operon is a group of genes that codifies for a group of enzymes that have the ability to digest lactose in order to use the energy in it. The lac operon will be active only when there is no glucose in the system to use it as an energy source, if there is glucose the lac operon will be inactive and if there is glucose and lactose the lac operon will also be inactive due to the fact that the bacteria prefers glucose.