Question

1.

A lac operon of genotype lacI- lacP+ lacO+ lacZ- lacY+ will produce b-galactosidase AND permease when

	lactose is present
	lactose is absent
	in the presence OR absence of lactose
	when glucose is present
	never

2. A lac operon of genotype lacI+ lacP+ lacO+ lacZ+ lacY- will produce b-galactosidase BUT NOT permease when

	lactose is present
	lactose is absent
	in the presence OR absence of lactose
	when glucose is present
	all of the above

Answer 1

Q.1

Option - Never.

The repressor LacI is mutated, so presence or absence of lactose has no influence on the gene expression.

LacZ gene is mutated hence functional b-galactosidase is not produced. Only functional permease is produced by the gene LacY.

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Q.2

Option - Lactose is present.

When lactose is present, it binds to the lactose binding site of repressor LacI and inhibits the repressor.

This is turn will produce functional b-galactosidase (LacZ) and non-functional permease (due to mutation in LacY).