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NEET Questions / Botany / Molecular Basis of Inheritance / Lac Operon
A mutant strain of E. coli is found where the repressor protein of the lac operon has lost its ability to bind to allolactose. In the presence of lactose, what would be the expected expression level of the lac operon genes in this mutant compared to a wild-type strain?
Higher than wild-type
Lower than wild-type
The same as wild-type
Completely absent
Imagine a scenario where glucose is absent, but a non-hydrolyzable analog of lactose is present in the medium. This analog can bind to the repressor but cannot be metabolized. Predict the level of lac operon expression compared to a wild-type strain in the presence of lactose and absence of glucose.
No expression
Basal level of expression
Similar level of expression
Significantly lower expression
A mutation in the lac operon's promoter region increases its affinity for RNA polymerase. In the presence of both glucose and lactose, how will the expression levels of the lac operon genes be affected compared to a wild-type strain?
No change in expression compared to wild-type.
Increased expression compared to wild-type, but not maximal expression.
Maximal expression of the lac operon genes.
Complete repression of the lac operon genes.
If a mutation occurs in the operator region of the lac operon such that the repressor protein can no longer bind, which of the following scenarios would still result in reduced lac operon expression compared to maximal induction?
Absence of glucose, presence of lactose
High glucose, presence of lactose
Absence of glucose, absence of lactose
High glucose, absence of lactose
In an environment containing both lactose and glucose, a mutation in the gene encoding adenylate cyclase renders it permanently inactive. What would be the primary consequence for lac operon expression?
Constitutive expression
Significantly reduced expression despite the presence of lactose
Expression levels similar to wild-type in the presence of only lactose
No change in expression compared to wild-type
A researcher engineers a strain of E. coli where the CAP binding site upstream of the lac operon promoter is deleted. In an environment lacking glucose and containing lactose, what would be the observed expression level of the lac operon genes compared to a wild-type strain under the same conditions?
Significantly reduced
Slightly reduced
No change
Significantly increased
Which of the following acts as the inducer in the lac operon?
Glucose
Galactose
Lactose
Fructose
What is the function of the operator in the lac operon?
Binding site for RNA polymerase
Binding site for the repressor protein
Codes for the repressor protein
Codes for ฮฒ-galactosidase
Which enzyme is responsible for breaking down lactose into glucose and galactose?
Lactase
Amylase
Sucrase
Maltase
In the absence of lactose, the lac repressor:
Binds to the promoter
Binds to the operator
Is inactive
Is degraded
