BIOL 2100 Chapter Notes - Chapter 18: Operon, Tryptophan, Repressor

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limesardine98

13 Nov 2016

School

University of Virginia

Department

Biology

Course

BIOL 2100

Professor

Kittlesen David

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8. 1 bacteria often respond to environmental change by regulating transcription. Enzymes react to chemical cues that increase or decrease catalytic activity. A(cid:272)ti(cid:448)it(cid:455) of first e(cid:374)z(cid:455)(cid:373)e i(cid:374) path(cid:449)a(cid:455) i(cid:374)hi(cid:271)ited (cid:271)(cid:455) path(cid:449)a(cid:455)"s e(cid:374)d produ(cid:272)t. If too much product created, enzyme activity inhibited: cells regulate gene expression. If enzyme activity needs to be turned off, control occurs at transcription level. Repressible and inducible operons: 2 types of negative gene regulation: trp opero(cid:374) e(cid:454)a(cid:373)ple of repressi(cid:271)le opero(cid:374) (cid:271)e(cid:272)ause it"s usuall(cid:455) o(cid:374) a(cid:374)d tur(cid:374)ed off (cid:449)he(cid:374) small molecule (tryptophan) binds to regulatory protein. In absence of lactose, the repressor is active and the lac operon genes are silenced. If lactose present, the inducer binds to repressor and alters shape so that the repressor cant bind to the operator: regulation of both types involves negative control because operons are switched off by active form of repressor protein.

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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BIOL 2100 Chapter Notes - Chapter 18: Operon, Tryptophan, Repressor

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