Control of Gene Expression

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Questions and Answers

Which level of gene expression regulation primarily occurs in prokaryotes?

Post-translational control

Post-transcriptional control

Translational control

Transcriptional control (correct)

What is the function of the lacZ gene in the lac operon of E. coli?

Moves lactose into the cell

Acetylates lactose

Hydrolyzes lactose to galactose + glucose (correct)

Regulates structural gene activity

Which of the following is NOT a regulatory element in the lac operon of E. coli?

Promoter region

Catabolite activator protein (CAP)

Operator

Enhancer (correct)

In the absence of lactose and presence of glucose, what is the outcome for the lac operon in E. coli?

Lac operon is repressed (turned off) Signup and view all the answers

What is the function of allolactose in the lac operon of E. coli?

Binds repressor protein Signup and view all the answers

Which of the following is a structural motif through which proteins bind DNA?

Zinc finger Signup and view all the answers

What is the main function of regulatory sequences in gene expression?

Control transcription Signup and view all the answers

Which of the following is NOT a condition under which the lac operon is involved in lactose metabolism?

lac +, glu++ Signup and view all the answers

What is the role of allolactose in lactose metabolism?

It acts as a regulatory element in the lac operon. Signup and view all the answers

What is the role of the Stringent Factor in the Stringent Response?

It is involved in the regulation of gene expression under stressful conditions. Signup and view all the answers

Under what condition does the trp operon initiate transcription?

trp high and initiates transcription Signup and view all the answers

What is the role of attenuation in the regulation of the trp operon?

It regulates the initiation of transcription in the trp operon. Signup and view all the answers

What are the three structural motifs proteins use to bind to the DNA?

Helix-turn-helix, zinc finger, and leucine zipper Signup and view all the answers

What is the role of STF in coordinate regulation using the example of the Galactose circuit in Yeast?

It coordinates the regulation of gene expression in the Galactose circuit in Yeast. Signup and view all the answers

Which of the following is true about mRNA stability?

mRNA stability can influence how much protein is produced Signup and view all the answers

What happens to the mRNA for TfR when the iron concentration in the cell is low?

It becomes more stable and is synthesized Signup and view all the answers

What is the function of microRNA (miRNA) in RNA interference (RNAi)?

They repress translation of target mRNA Signup and view all the answers

What is the role of Drosha in the processing of microRNA (miRNA)?

It processes pri-miRNA into pre-miRNA Signup and view all the answers

How are histones modified to allow access for RNA polymerase?

Acetylation of histones increases association with DNA Signup and view all the answers

What is the role of transcription factors in gene regulation?

They enhance RNA polymerase binding to the promoter Signup and view all the answers

What is the function of coactivators (mediator proteins) in gene regulation?

They enhance assembly of the basal transcription complex Signup and view all the answers

What is the role of specific transcription factors in gene regulation?

They increase transcription of a gene when bound to enhancers Signup and view all the answers

How is gene expression regulated in eukaryotes?

Primarily at the level of initiation of gene transcription Signup and view all the answers

Which of the following statements regarding the Lac operon in E. coli is true?

The Lac operon is induced when lactose is present and glucose is absent. Signup and view all the answers

Which of the following is a characteristic of transcriptional attenuation in the trp operon in E. coli?

Transcription is initiated but terminated before completion. Signup and view all the answers

What happens in the trp operon when tryptophan levels are high?

The operator is bound by the repressor, resulting in repression of the operon. Signup and view all the answers

What is the function of the stringent response in E. coli?

Regulation in response to amino acid starvation. Signup and view all the answers

How does coordinate regulation of a group of genes for a specific response occur in eukaryotes?

A specific transcription factor binds to cis-acting regulatory elements on each gene in the group. Signup and view all the answers

How is the expression of genes involved in metabolizing galactose coordinated in yeast?

Coordinated expression is mediated by the Gal4 transcription factor. Signup and view all the answers

What is the function of intracellular receptors in the hormone response system?

Intracellular receptors bind to hormones and regulate gene expression. Signup and view all the answers

Study Notes

Gene Expression Regulation

Transcriptional regulation primarily occurs in prokaryotes.

Lac Operon in E.coli

The lacZ gene encodes β-galactosidase, which converts lactose into glucose and galactose.
In the absence of lactose and presence of glucose, the lac operon is inhibited.
Allolactose is an inducer that binds to the lac repressor, allowing transcription of the lac operon.
The lac repressor binds to the operator sequence to inhibit transcription.

Regulatory Elements

Helix-turn-helix and zinc finger motifs are structural motifs used by proteins to bind DNA.
Regulatory sequences, such as promoters and enhancers, recruit RNA polymerase and transcription factors to initiate transcription.

Trp Operon

The trp operon initiates transcription when tryptophan levels are low.
Attenuation, a type of transcriptional regulation, occurs in the trp operon through the formation of stem-loop structures.

RNA Interference (RNAi) and Regulation

MicroRNA (miRNA) is involved in RNAi, silencing specific genes by binding to mRNA.
Drosha is an enzyme that processes miRNA.
Histone modification, such as acetylation, allows RNA polymerase access to DNA.

Transcription Factors and Coactivators

Transcription factors bind to specific DNA sequences to initiate transcription.
Coactivators (mediator proteins) bridge transcription factors and RNA polymerase, enhancing transcription.
Specific transcription factors regulate gene expression in response to specific signals.

Gene Regulation in Eukaryotes

Gene regulation in eukaryotes involves multiple levels of regulation, including transcriptional, post-transcriptional, and translational regulation.

Coordinate Regulation

Coordinate regulation of a group of genes occurs through specific transcription factors and coactivators.
In yeast, the galactose circuit involves coordinate regulation of genes involved in galactose metabolism.

Hormone Response System

Intracellular receptors bind to hormones, triggering a response that regulates gene expression.

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Description

This quiz tests your knowledge on the regulation of gene expression in E. coli, specifically focusing on the lactose (lac) operon and the tryptophan (trp) operon. It covers topics such as the role of adenylyl cyclase, the binding of RNA polymerase, and the expression of proteins.