REGULATION OF THE GENE EXPRESSION 2

Question 1

Mutations in the LacZ or LacY genes result in?

Answer 1

in a loss of either (but not both) activities, and these mutations were recessive

• Thus, loss of the genes encoding either enzyme results in a lack of the respective activity- LacZ and
• LacY are structural genes that encode the amino acid sequence of the respective enzymes

Question 2

A recessive mutation in a linked gene, LacI, resulted in?

Answer 2

high levels of LacZ and LacY even in the absence of inducer (i. e. constitutive expression).

Question 3

What two different kinds of elements are present in the lac operon’s regulation?

Answer 3

DNA binding sites (LacP, LacO, Pi),

Proteins (CAP, LacI, and LacZ, LacY, and LacA).

Question 4

Cis dominant mutations in the Lac operator resulted in?

Answer 4

constitutive high level expression of both LacZ and LacY.

Question 5

Cis dominant mutations in the lactose promoter result in

Answer 5

a lack of expression of both the LacZ and LacY genes.

Question 6

Catabolite Activator Protein (CAP) turns?

Answer 6

the Lac genes on when glucose is not present.

Question 7

ARABINOSE OPERON

Answer 7

is responsible for the ability of the cell to use the sugar arabinose as a carbon source

Question 8

The ara operon is only expressed? (In /When)

Answer 8

1) In the presence of the substrate arabinose. and

2) When levels of the preferred carbon source glucose is low.