BIOB11H3 Lecture Notes - Lecture 9: Dna Replication, Beta-Galactosidase, Lac Repressor

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24 Oct 2017

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Lec 09: gene regulation i: promoters and control circuits. Operon: a unit made up of linked genes that is thought to regulate other genes responsible for protein synthesis. Repressor: a repressor is a dna- or rna-binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. A dna-binding repressor blocks the attachment of rna polymerase to the promoter, thus preventing transcription of the genes into messenger rna. Co-repressor: a corepressor is a substance that inhibits the expression of genes. In prokaryotes, corepressors are small molecules whereas in eukaryotes, corepressors are proteins. Derepression: a repressor gene inhibits the activity of an operator gene. Removal of repression, such as of an operon so that gene transcription occurs or is enhanced, with the net result frequently being elevation of the level of a speci c enzyme. Inducer: an inducer is a molecule that regulates gene expression. An inducer can bind to protein repressors or activators.

Related Questions

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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BIOB11H3 Lecture Notes - Lecture 9: Dna Replication, Beta-Galactosidase, Lac Repressor

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