Question

To complete the table,below, consider the following elements of the system:

[lacI promoter, lacI protein coding region, lacZ/Y promoter, lacZ protein coding for B-Galactotosidase, lacY protein coding for Permease, and operator]

Complete the table by using the pull down menu to select for “+” or “-“ symbols to show if β-Galactotosidase or Permease protein are produced in bacteria with the follow genotypes.

(For Reference)	B-Galactotosidase (lacZ)		Permease (lacY)
	No Lactose	Lactose Present	No Lactose	Lactose Present
lacPI+ lacI+ lacPzya+ lacO+ lacZ+ lacY+
lacPI- lacI+ lacPzya+ lacO+ lacZ+ lacY+
lacPI+ lacIS lacPzya+ lacO+ lacZ- lacY+
lacPI+ lacIS lacPzya+ lacOC lacZ+ lacY-

Answer 1

lac repressor inhibits the expression of the lac operon if the inducer is absent, lactose is an inducer of the lac operon when the lactose is present lac repressor is inhibited by lactose, so lac operon can be expressed.

lacPI+ - promoter of lac I gene.

lacI+ - functional lac I gene that codes for lac repressor.

lacPzya+ - promoter of lac operon.

lacO+ -lac operator.

lacZ+- codes for beta-galactosidase

lacY+ - codes for permease.

	Beta-galactosidase	Permease
	lactose present	lactose absent	lactose present	lactose absent
lacPI+ lacI+ lacPzya+ lacO+ lacZ+ lacY+	lactose inhibits the lac repressor so lac operon is expressed, beta-galactosidase is produced. +	lac repressor inhibits lac operon -	lactose inhibits the lac repressor so lac operon is expressed,+	lac repressor inhibits lac operon -
lcPI- lacI+ lacPzya+ lacO+ lacZ+ lacY+	the promoter of lac repressor is mutated so lac repressor is not produced, so lac operon is expressed even if lactose is absent or not. +	the promoter of lac repressor is mutated so lac repressor is not produced, so lac operon is expressed even if lactose is absent or not. +	the promoter of lac repressor is mutated so lac repressor is not produced, so lac operon is expressed even if lactose is absent or not. +	the promoter of lac repressor is mutated so lac repressor is not produced, so lac operon is expressed even if lactose is absent or not. +
lacPI+ lacIS lacPzya+ lacO+ lacZ- lacY+	lac Is gene is present it is super repressor which inhibits the expression of the lac operon because it cannot be inhibited by the inducer, it has a mutation in the inducer binding domain, so lac operon is not expressed, none of the gene in the lac operon is expressed even if lactose is present.-	lac Is gene is present it is super repressor which inhibits the expression of the lac operon because it cannot be inhibited by the inducer, it has a mutation in the inducer binding domain, so lac operon is not expressed, none of the gene in the lac operon is expressed even if lactose is present.-	lac Is gene is present it is super repressor which inhibits the expression of the lac operon because it cannot be inhibited by the inducer, it has a mutation in the inducer binding domain, so lac operon is not expressed, none of the gene in the lac operon is expressed even if lactose is present.-	lac Is gene is present it is super repressor which inhibits the expression of the lac operon because it cannot be inhibited by the inducer, it has a mutation in the inducer binding domain, so lac operon is not expressed, none of the gene in the lac operon is expressed even if lactose is present.-
lacPI+ lacIS lacPzya+ lacOC lacZ+ lacY-	lac Is gene is present it is super repressor which inhibits the expression of the lac operon because it cannot be inhibited by the inducer, but the operator is constitutive so lac operon cannot be inhibited by lac repressor, so lac operon is expressed always and it has functional lac Z gene so beta-galactosidase is expressed always  +	lac Is gene is present it is super repressor which inhibits the expression of the lac operon because it cannot be inhibited by the inducer, but the operator is constitutive so lac operon cannot be inhibited by lac repressor, so lac operon is expressed always, and it has functional lac Z gene so beta-galactosidase is expressed always  +	lac Is gene is present it is super repressor which inhibits the expression of the lac operon because it cannot be inhibited by the inducer, but the operator is constitutive so lac operon cannot be inhibited by lac repressor, so lac operon is expressed always but lacY gene is mutated so permease cannot be produced, under any condition -	lac Is gene is present it is super repressor which inhibits the expression of the lac operon because it cannot be inhibited by the inducer, but the operator is constitutive so lac operon cannot be inhibited by lac repressor, so lac operon is expressed always but lacY gene is mutated so permease cannot be produced, under any condition -