2.Below are possible alleles found in the lac operon. Repressor gene Is (superre

Question

2.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) Which of the following combination(s) below is/are constitutive and will express beta-galactosidase even when lactose is absent (circle them)? Explain why for each of the answer that you circled. (6 points)

Explanation / Answer

lac operon , It is an operon required for metabolism and transport of lactose .It is polycystronic mRNA.

lac i gene is the regulatory gene for the lac operon produces a protein that blocks the RNA polymerase from binding of the promoter of the operon ,THi sprotein can be removed only when it binds allolactose binds to it and inactivates to it . The protein which binds to lac I gene is called repressor .

allolactose ; It is an isomer of the lactose and is the inducer of the lacoperon ,lactose is converted into the allolactose by the enzyme beta galactosidase .

I- Oc ; they can produce the enzyme even in the absence of the lactose as the inducer cannot bind to the repressor molecule so there will be contineous production of the enzyme betagalosidase even in the absence of the lactose .

Is Oc ; The are not constitutive , it cannot produce enzyme continuously as the supresssor can bind to the operator

I+ O+ ; It is constitutive as the inducer can convert the allolactose to lactose there by the repressor molecule cannot bind to operator there contineuous production of the betagalactosidase .

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