Microbial Regulatory System (Lec #9)

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Questions and Answers

Which enzyme is responsible for DNA replication?

Ribosome

DNA polymerase (correct)

tRNA

RNA polymerase

Which molecule is the template for RNA synthesis during transcription?

DNA (correct)

tRNA

mRNA

Ribosome

What is the major mode of regulation for gene expression in bacteria?

Translation

Post-translational modification

Transcription (correct)

Gene organization

What is the function of mRNA during protein synthesis?

Template for protein synthesis Signup and view all the answers

What is the role of tRNA during protein synthesis?

Brings amino acids to the ribosome Signup and view all the answers

What is the function of RNA polymerase?

Catalyzes transcription of DNA into RNA Signup and view all the answers

What is an operon in bacteria?

A group of genes transcribed into a single mRNA Signup and view all the answers

Which type of control mechanism prevents the synthesis of an enzyme in response to a signal?

Repression Signup and view all the answers

What is the effector molecule called that binds to the repressor and alters its conformation in the mechanism of repression?

Co-repressor Signup and view all the answers

Which type of control mechanism involves the production of an enzyme in response to a signal?

Induction Signup and view all the answers

What is the effector molecule that binds to the repressor and alters its conformation in the mechanism of induction?

Inducer Signup and view all the answers

What is the regulatory protein that binds to an activator binding site near the promoter and helps RNA polymerase bind to the DNA in positive control?

Activator Signup and view all the answers

What is the term for multiple operons controlled by the same regulatory protein?

Regulon Signup and view all the answers

What is the mechanism of an activator that involves bending DNA to allow for RNA polymerase binding?

Looping Signup and view all the answers

Which sigma factor triggers sporulation in Bacillus subtilis?

Spo0A Signup and view all the answers

What controls endospore formation?

Sigma Factors Signup and view all the answers

In Quorum Sensing what was the first autoinducer identified?

Acyl Homoserine lactones (AHLs) Signup and view all the answers

Which of the following is true about catabolite repression in prokaryotes?

Catabolite repression ensures that the 'best' carbon and energy source is used first Signup and view all the answers

Which protein acts as an activator in catabolite repression?

Cyclic AMP receptor protein (CRP) Signup and view all the answers

What happens to cyclic AMP levels when glucose levels are high?

Cyclic AMP levels decrease Signup and view all the answers

What is the role of the lac repressor in the lac operon?

It binds to the operator and prevents transcription of the lac genes Signup and view all the answers

What is the function of the sensor kinase in a two-component regulatory system?

It detects a signal from the environment and phosphorylates itself Signup and view all the answers

What is the purpose of quorum sensing in prokaryotes?

To monitor population size and control gene expression based on cell density Signup and view all the answers

What is the role of sigma factors in gene expression control?

They interact with consensus sequences at the promoter Signup and view all the answers

Study Notes

DNA Replication and Transcription

DNA replication is primarily facilitated by the enzyme DNA polymerase.
Messenger RNA (mRNA) is synthesized using DNA as a template during transcription.

Gene Expression Regulation in Bacteria

Gene expression in bacteria is majorly regulated through operons.
Transcriptional regulation can prevent enzyme synthesis in response to environmental signals (known as repression).

mRNA and tRNA Functions

mRNA serves as the template during protein synthesis, conveying the genetic code from DNA.
Transfer RNA (tRNA) functions to transfer specific amino acids to the ribosome during protein synthesis.

RNA Polymerase Function

RNA polymerase synthesizes RNA from the DNA template during transcription.

Operons and Control Mechanisms

An operon is a cluster of genes under the control of a single regulatory protein.
A control mechanism that prevents enzyme synthesis in response to a signal is known as negative control.
Effector molecules that bind to repressors and alter their conformation in repression are called corepressors.
Induction involves the production of enzymes in response to a signal, utilizing inducers as effector molecules.

Positive Control in Gene Regulation

In positive control, regulatory proteins bind to activator binding sites to enhance RNA polymerase binding to DNA.
The term for multiple operons controlled by the same regulatory protein is polycistronic operon.

Mechanisms of Activation and Sporulation

An activator can bend DNA to facilitate RNA polymerase binding, assisting in transcription initiation.
The sigma factor that triggers sporulation in Bacillus subtilis is sigma factor F (σF).
Endospore formation is controlled by various environmental factors and specific regulatory pathways.

Quorum Sensing and Autoinducers

The first autoinducer identified in Quorum Sensing was N-acyl homoserine lactone (AHL).
In prokaryotes, catabolite repression is a mechanism regulating the use of different carbon sources.

Catabolite Repression and cAMP

In prokaryotes, catabolite repression involves inhibition of certain enzyme synthesis when preferred carbon sources, like glucose, are present.
When glucose levels are high, cyclic AMP (cAMP) levels decrease, hindering activation of certain operons.

Lac Operon and Sensor Kinases

The lac repressor binds to the lac operon in the absence of lactose, inhibiting transcription.
In two-component regulatory systems, the sensor kinase detects environmental signals and modulates cellular responses.

Quorum Sensing Purpose

Quorum sensing enables prokaryotic cells to communicate based on population density, coordinating collective behaviors.

Sigma Factors and Gene Expression

Sigma factors are proteins that direct RNA polymerase to specific promoters, playing a vital role in controlling gene expression.

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Description

Test your knowledge on global control and the lac operon with this quiz! Explore topics such as catabolite repression, activator proteins, and the role of RNA polymerase in regulating catabolic operons. Challenge yourself and see how well you understand the intricacies of allosteric regulation and the utilization of different carbon and energy sources.