Question

Below is the genotype for a partial diploid E.coli strain. Answer the following questions by filling in the blank with either "yes" or "not". Assume that glucose is absent in all situations.

I^-O^cZ⁺Y^-/I⁺O⁺Z^-Y^-

Is functional β-galactosidase produced when lactose is in the cell?

  Is functional β-galactosidase produced when there is no lactose in the cell?

Assume an E. coli cell is in an environment that contains both glucose and lactose. Will the lac operon be fully expressed in these conditions?

	a.	No
	b.	Yes

Assume an E. coli cell is in an environment that contains both glucose and lactose. Regarding the lac operon, what will be the state of the lac repressor protein?  Choose any that apply.

	a.	Bound to the promoter
	b.	Bound to the operator
	c.	Bound to lactose
	d.	Bound to cAMP

An operon in E. coli called the Gua operon, encodes proteins responsible for guanine biosynthesis. Two genes, guaA and guaB are under the control of a single promoter and operator, similar to the arrangement in the lac and trp operons. A repressor protein, purR, binds to the operator. Is this a "repressible" or an "inducible" operon?

	a.	Repressible
	b.	Inducible

An operon in E. coli called the Gua operon, encodes proteins responsible for guanine biosynthesis. Two genes, guaA and guaB are under the control of a single promoter and operator, similar to the arrangement in the lac and trp operons. A repressor protein, purR, binds to the operator. In what conditions (high guanine or low guanine) do you suppose this repressor binds to the operator?

	a.	High levels of guanine
	b.	Low levels of guanine

  Is functional permease produced when lactose is in the cell?

  Is functional permease produced when there is no lactose in the cell?

Answer 1

question 1 Is functional β-galactosidase produced when lactose is in the cell?

True, because if lactose is added to the growth medium there is a gradual accumulation of β-galactosidase within the bacterium.

question 2 Is functional β-galactosidase produced when there is no lactose in the cell?

false, n the absence of lactose, the lac repressor, lacI, halts production of the enzymes encoded by the lac operon

question 3

When glucose and lactose both are present,Low-level transcription of the lac operon occurs. The lac repressor is released from the operator because the inducer (allolactose) is present. cAMP levels, however, are low because glucose is present. Thus, CAP remains inactive and cannot bind to DNA, so transcription only occurs at a low, leaky level. So answer is false.

question 4

bound to lactose as The lac repressor is released from the operator because the inducer (allolactose) is present. Allolactose is a disaccharide similar to lactose.