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Amino Acids

Which of the ...

Question

Which of the following scenarios occurs when lactose is present as the sole energy source?

A

Production of the repressor protein is increased.

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B

The enzymes for lactose metabolism are produced.

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C

The repressor protein binds to the operator.

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D

The lac operon genes are not transcribed.

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Solution

The correct option is B The enzymes for lactose metabolism are produced.
When lactose is present it binds to the repressor protein.
Binding of the repressor protein by lactose causes the repressor protein to be released from the operator.
When the repressor protein is gone, RNA polymerase is free to bind to the promoter and transcribe the enzymes for lactose metabolism.

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Q. Which of the following statements are true about lac operon?
I. In the absence of lactose, the repressor binds with the operator region.
II. All three structural genes in the operon are not essential for the metabolism of lactose.
III. The operator is a negative regulatory site bound by the lac repressor protein.

Q. Which of the following statements are true about lac operon?
I. Glucose binds to CAP binding site and activates the operon
II. In the absence of lactose, the repressor binds with the operator region
III. All three structural gene products are not essential for the metabolism of lactose
IV. The operator is a negative regulatory site bound by the lac repressor protein

Q. Operon is a coordinated group of genes that function together as a unit for a metabolic pathway. How many statements below are correct with respect to lac operon?
i) Glucose or galactose may bind with the repressor and inactivate it.
ii) In the absence of lactose, the repressor binds with the operator region.
iii) The Z-gene codes for permease.
iv) I- gene codes for repressor protein

Q. Match the component of 'lac operon' of E.coli given under column-I with their function listed in column-II. Choose the answer with the correct combination of alphabet of the two columns:

Column-I	Column-II
(A) Structural gene	(i) Binding site for a repressor protein
(B) Operator gene	(ii) Codes for a repressor protein
(C) Promoter gene	(iii) Induce lactose transport from the medium
(D) Regulator gene	(iv) Codes for protein enzyme
	(v) Binding site for RNA polymerase

Q. Read the statements regarding the lac operon and choose the correct option
I. An inducer regulates the switching on and off of lac operon.
II.Repressor protein dissociates from operator region and prevents RNA polymerase from transcribing the operon.
III. In the presence of lactose, the repressor is activated by interaction with lactose.
IV. RNA polymerase has access to the promoter and transcription proceeds only when the repressor is inactivated.

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