Nucleic Acids - Mock Test 26

Question 251

Transcription of structural genes of lac operon is prevented by binding of the repressor tetramer to?

A) i gene B) Operator locus C) Promoter D) z gene

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Question 252

Trancription of z, y and a genes of lac operon is prevented by?

A) Lactose B) Allo-lactose C) Repressor D) cAMP

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Question 253

RNA polymerase holoenzyme binds to lac operon at the following site?

A) i gene B) z gene C) Operator locus D) Promoter region

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Question 254

The regulatory i gene of lac operon?

A) Is inhibited by lacotse B) Is inhibited by its own product, the repressor protein C) Forms a regulatory protein which increases the expression of downstream structural genes D) Is constitutively expressed

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Question 255

Lac operon is a cluster of?

A) Three structural genes B) Three structural genes and their promoter C) A regulatory gene, an operator and a promoter D) A regulatory gene, an operator, a promoter and three structural genes

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Question 256

Lac operon is a cluster of genes present in?

A) Human beings B) E. coli C) Lambda phage D) All of these

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Question 257

Proteins which interact with DNA and affect the rate of transcription possess the following structural motif?

A) Helix-turn-helix motif B) Zinc finger motif C) Leucine zipper motif D) All of these

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Question 258

Amplification of dihydrofolate reductase gene may be brought about by?

A) High concentrations of folic acid B) Deficiency of folic acid C) Low concentration of thymidylate D) Amethopterin

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Question 259

Enhancer elements have all the following features except?

A) They increase gene expression through a promoter B) Each enhancer activates a specific promoter C) They may be located far away from the promoter D) They may be upstream or downstream from the promoter

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Question 260

trans-acting factors include?

A) Promoters B) Repressors C) Enhancers D) Silencers

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