How do you get the answers below? 3. (12 points) For the following E. coli strai

Question

How do you get the answers below?

3. (12 points) For the following E. coli strains, determine if wild-type Z and Y proteins are always made , never made, or only made in the presence of lactose lac Z: Always made Never made Only made winducer_X lac Y: Always made Never made_ X___ Only made w/inducer : lac Z: Always made- _XNever made Only made w/inducer lac Y: Always made Never made_ Only made w/inducer lac Z: Always made Never made X_Only made w/inducer lac Y: Always made Never made Only made winducer lac Z: Always made_XNever made Only made w/inducer lac Y: Always made Never made_ X___ Only made w/inducer : lac Z: Always made Never made Only made w/inducer lac Y: Always made Never made Only made w/inducer lac Z: Always made Never made Only made w/inducer lac Y: Always made Never made Only made w/inducer,

Explanation / Answer

Gene/element

Function

Mode of control

ß-gal (lacZ)

lacZ+

Normal gene

-

lacZ-

Affects the structure of enzyme - nonfunctional

-

Permease (lacY)

lacY+

Normal gene

-

lacY-

Affects the structure of enzyme - nonfunctional

-

Trancetylase (lacA)

lacA+

Normal gene

-

lacA-

Affects the structure of enzyme - nonfunctional

-

Operator (lacO)

lacO+

Normal operator

Cis

lacOc

Constitutive operator, repressor cannot bind to Constitutive operator

Cis

Promoter (lacP)

lacP+

Normal promoter

Cis

lacP-

RNA polymerase cannot bind

Cis

Repressor (lacI)

lacI+

Normal repressor

Trans

lacI-

Repressor is not produced

Trans

lacIs

Superrepressor, it cannot be inactivated by inducer

Trans

a.
Lac Z gene: as the Z gene is normal gene in first gene, and the repressor is functional, this will be inactivated by inducer and the Z gene will be induced. Hence the answer is only made wit inducer.

Lac Y gene: As the Y in first gene is mutant and promoter is non functional in the second gene, lac Y never made its product.

b.
Lac Z gene: As the first gene has constititive operator, the repressor cannot bind, so the Z gene expresses continously. The answer is always made

Lac Y gene: The y gene in first DNA is not functional and due to the presence of non functional promoter (RNA cannot binds it) the y gene is never expressed.

Gene/element

Function

Mode of control

ß-gal (lacZ)

lacZ+

Normal gene

-

lacZ-

Affects the structure of enzyme - nonfunctional

-

Permease (lacY)

lacY+

Normal gene

-

lacY-

Affects the structure of enzyme - nonfunctional

-

Trancetylase (lacA)

lacA+

Normal gene

-

lacA-

Affects the structure of enzyme - nonfunctional

-

Operator (lacO)

lacO+

Normal operator

Cis

lacOc

Constitutive operator, repressor cannot bind to Constitutive operator

Cis

Promoter (lacP)

lacP+

Normal promoter

Cis

lacP-

RNA polymerase cannot bind

Cis

Repressor (lacI)

lacI+

Normal repressor

Trans

lacI-

Repressor is not produced

Trans

lacIs

Superrepressor, it cannot be inactivated by inducer

Trans

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