Below are possible alleles found in the lac operon. ---------------------- Repre

Question

Below are possible alleles found in the lac operon.

----------------------   

Repressor gene

Is (superrepressor; can’t bind allolactose, but can bind operator)

I+ (inducible; wild-type)

I- (constitutive; can bind allolactose, but can’t bind operator)

Operator

Oc (constitutive; can’t bind repressor)

O+ (inducible; wild-type)

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Which of the following combination(s) below is/are constitutive and will express ?-galactosidase even when lactose is absent?

Question 3 options:

IsO+   

This cannot be determined

I-Oc   

I+O+   

IsO+   

This cannot be determined

I-Oc   

I+O+   

Explanation / Answer

we want a combination(s) is/are constitutive and will express ?-galactosidase even when lactose is absent.

in the absence of lactose, repressor binds to the operator and lac operon is inactive. so to overcome this situation operator must be constitutive so that repressor will not be able to bind. also the product of repressor gene will not be able to bind to the operator.

from the above given option, option 3 is correct. I-Oc.

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