Question

Question 35 8 pts For each of the following cells, indicate (circle) if lacZ is predicted to be expressed in absence of lactose by typing YES or NO. (8 points) Chromosomal Alleles F' Alleles lacZ expression A. lacl+ lacO+ lacZ+ none B. lacl- lacO+ lacZ+ none C. lacl+ lacO+ lacZ+ lacl+ laco lacZ+ D. lacl+ lacO+ lacZ+ lacl+ laco lacz-

Answer 1

Ans- lacI encodes for the repressor of lac operon. LacO is the operator where repressor binds. LacZ encodes for enzyme $\beta$ -galactosidase.

In the absence of lactose, repressor binds operator and no expression of LacZ occurs.

In presence of lactose, the lactose binds repressor so, repressor does not bind operator and hence, LacZ is expressed.

+ represents the gene is functional while - represents gene is non-functional and c represents constitutive expression or continuous expression. This expression is unaffected by presence or absence of repressor.

A. No

Because repressor is expressed and also lactose is absent.

B. Yes

Because repressor is absent. LacI is negative.

C. Yes

Because the operator shows constitutive expression.

D. No

Because under constitutive operator, LacZ is not expressed and one with LacZ positive has its repressor present. Repressor can act on other genes but operator are able to work on genes near to it.