MCB 3020L Lecture Notes - Lecture 30: Corepressor, Cyclic Adenosine Monophosphate, Lac Operon

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28 Mar 2018

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Decreases the synthesis of enzymes and inhibits gene expression due to an overabundance of an end product of a metabolic pathway. Mediate repression and block the ability of rna polymerase to initiate transcription from the repressed genes. What is the default position of a repressible gene on. Induction rocess that turns on the transcription of a gene or genes. Substance that acts to induce transcription of a gene and is usually in the off position. Details of control of gene expression which is based on studies of e. coli. Consists of the promoter and operator site and structural genes that code for the protein. Region of dna where rna polymerase intitates transcription. Acts as a traffic light that acts as a go ro stop signal for transcription of the structural genes. A set of operator and promotor sites and the structural genes they control. Protein that switches inducible and repressible oerpons on or off.

Related Questions

Fill in the blank:

promotor, induction, presence, will not, will, operon, repressor, repression, overabundance, operator, control region,

1. If the repressor is bound to the operator, then RNA polymerase______ transcribe the structural genes.

2. The ________ controls whether RNA polymerase can advance along the DNA strand or not.

3. The _______ operates differently depending on whether the operon is inducible or repressible.

4. An _________ controls the expression of functionally related genes and consists of a control region and structural genes.

5. ______ decreases expression of the structural genes. This typically occurs in response to an _____ of a substrate.

6. The _____ contains a promoter and an operator.

7. If the repressor is not bound to the operator, then RNA polymerase _____ transcribe the structural genes.

8. ______ increases expression of the structural genes. This typically occurs in response to the _______ of a substrate.

9. The ______ is the region of DNA where RNA polymerase initially binds.

1.) What type of control best describes the lac operon when it is regulated by allolactose? Explain the features of this type of regulation using the lac operon as an example.

2.) What is positive gene regulation?

a) when an activator protein binds to the operator of a gene to turn expression off

b) when a repressor protein binds to the operator of a gene to turn expression off

c) when an activator protein binds to the operator of a gene to turn expression on

d) when a repressor protein binds to the operator of a gene to turn expression on

e) when a protein binds to DNA to change gene expression

3.) In the lactose operon of E. coli, what is the function of each of the following genes or sites: a) regulator, b) operator, c) promoter, d) structural gene Z and e) structural gene Y?

a) regulator gene

b) operator

c) promoter

d) structural gene Z

e) structural gene Y

4.) In a negative, repressible regulatory mechanism, transcription of the structural gene(s) occurs in

a) the presence of the co-repressor, but not in its absence.

b) the absence of the co-repressor, but not in its presence.

c) the presence of the inducer, but not in its absence.

d) the absence of the inducer but not in its presence.

e) the absence or presence of the co-repressor.

What are answers and can you explain them to me?

1. What is the term when the product of a biochemical pathway inhibits the activity of the first enzyme of a pathway?

		feedback inhibition.
		activator inhibition.
		diffusional regulation.
		enzyme activation.

2. Through control of gene expression, prokaryotes respond to changing __________ conditions.

		internal
		protein
		environmental
		genetic

3. A protein that negatively regulates transcription by binding to the operator is known as the

		operon
		repressor
		activator
		inducer

4. During attenutation, when tryptophan levels are high, the ________ stem-loop forms and transcription ________ the trpL gene.

		1-2, ends just past
		3-4, ends just past
		1-2, continues beyond
		3-4, continues beyond

5. The process of turning on the expression of a gene in response to a substance in the environment is called:

		constituation.
		repression.
		induction.
		catabolism.

6. What is a function of some specific transcription factors?

		to bind to the promoter region of the gene to facilitate the proper alignment of the RNA polymerase
		to bind to the centromere to induce meiosis
		to bind to enhancer regions to help regulate gene transcription
		to bind to the operator to recruit sigma factor

7. How does exposing an E.coli cell to glucose affect the regulation of the lac operon via CAP?

		cAMP binds to CAP and transcription is increased.
		cAMP binds to CAP and transcription is decreased.
		cAMP does not bind to CAP and transcription is increased.
		cAMP does not bind to CAP and transcription is decreased.

8. The lac repressor protein works when mutations in the repressor gene and structural genes are:

		in cis or in trans.
		in trans only.
		in cis only.
		in both prokaryotes and eukaryotes.

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MCB 3020L Lecture Notes - Lecture 30: Corepressor, Cyclic Adenosine Monophosphate, Lac Operon

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