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+  / F'  lacPI+ lacIS
lacPI+ lacI+ lacPzya- lacO+ lacZ+ lacY+ / F' lacPI+ lacI- lacPzya+ lacOC lacZ- lacY-
lacPI+ lacIS lacPzya+ lacO+ lacZ+ lacY- / F' lacPzya+ lacOC lacZ+ lacY+
lacPI+ lacI- lacPzya+ lacOC lacZ+ lacY- / F' lacPI+ lacI+ lacPzya+ lacO+ lacZ- lacY+

Answer 1

Mutant lacIS is super repressor, where lactose cannot bind to repressor and transcription of lac Z and lac Y is inhibited in presence as well as absence of lactose (even in partial diploid)

Mutant lacOC is constitutive cis acting mutant-with non-functional operator because of which repressor will not bind and transcription will continue in presence as well as absence of lactose.