The Accompanying Table Lists Several Genotypes Associated with the Lac $\beta$

question 40

Essay

The accompanying table lists several genotypes associated with the lac operon in E. coli. For each, indicate with a "+" or a "-" whether β-galactosidase would be expected to be produced at induced levels. Genotype                         $\beta$ -galactosidase production
                                        No Lactose         With Lactose
(a) $\quad I + O + Z + / F ^ { \prime } I + O + Z +$
(b) $\quad I - O c Z - / F ^ { \prime } I - O c Z -$
(c) $\quad I - O c Z + / F ^ { \prime } I - O + Z +$
(d) Is Oc $\mathrm { Z } - \mathrm { F } ^ { \prime }$ Is $\mathrm { O } + \mathrm { Z } ^ { + }$
$I ^ { + } =$ wild-type repressor
$I ^ { - } =$ mutant repressor (unable to bind to the operator)
Is $=$ mutant repressor (insensitive to lactose)
$\mathrm { O } ^ { + } =$ wild-type operator
$\mathrm { OC } =$ constitutive operator (insensitive to repressor)

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Definitions:

Yeasts

A diverse group of unicellular fungi that are widely used in baking, brewing, and biotechnology for their ability to ferment sugars.

Ediacaran Fauna

Refers to an assemblage of ancient, soft-bodied marine organisms that lived during the Ediacaran Period, approximately 635 to 541 million years ago.

Tetrapods

Vertebrate animals having four limbs or limb-like appendages, including amphibians, reptiles, birds, and mammals.

Lineages

Refers to lines of descent or ancestral sequences, often traced through generations of organisms to study evolutionary relationships.