BISC 202 Lecture Notes - Lecture 30: Lac Operon, Operon, Repressor

71 views12 pages

coffeegrasshopper724

5 Dec 2018

School

Simon Fraser University

Department

Biological Sciences

Course

BISC 202

Professor

Michael Hart

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Structural gene: a gene that codes for any rna or protein other than a regulatory protein: operon: a set (cluster) of structural genes that are coordinately regulated by a single promoter region (includes the promoter) in prokaryotes. During transcription, all structural genes are transcribed onto one mrna molecule. During translation, each gene is translated independently to produce different gene products: operator: a special sequence inside the operon, upstream of the transcription initiation point and overlaps with the promotor. Lac operon: has 3 genes, used by e. coli to produce 3 enzymes to digest lactose lacz: codes for -galactosidase lacy: codes for permease laca: codes for transacetylase. Laci gene: a gene located near the lac operon but not part of the operon. It has its own promoter and codes for the lac-repressor protein continuously (there is always lac repressor present in the cell) Regulatory proteins (eg. lac repressor): two sites for sense and respond .

Related Questions

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.In the T7/lac expression system used for ADH expression, which of the following is true?

The promoter for the ADH gene is specific for E. coli RNA polymerase.

The promoter for the ADH gene contains the lac operator sequence.

The pLacI plasmid encodes the T7 RNA polymerase gene.

All of the above

2.The ADH gene used in this lab contains

A his-tag at the N-terminus

An HSV tag near the N-terminus

A strep tag at the C-terminus

None of the above

3.During ADH expression in Tuner cells, which of the following occurs?

Binding of IPTG to the Lac repressor protein facilitates expression of the T7 RNA polymerase.

IPTG represses the expression of the Lac repressor protein.

The presence of glucose in the medium results in CAP-binding protein recruiting E. coli RNA polymerase to the T7 RNA polymerase gene.

All of the above

4. How would you interpret your NovaBlue transformation results if you saw no colonies on any of your plates (controls and experimental)?

You used the wrong cells for the transformation.

You used the wrong medium for the transformation.

You heat shocked the cells for too long.

Any of the above could explain the results.

5.In SDS-PAGE, which of the following is true?

The proteins are only negatively charged in the resolving gel.

The stacking gel has a higher pH than that of the resolving gel.

The concentration of acrylamide is higher in the stacking gel relative to the resolving gel.

none of the above

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.

scarletwombat949

BISC 202 Lecture Notes - Lecture 30: Lac Operon, Operon, Repressor

Document Summary

Get access

Related Documents

BISC 202 Lecture Notes - Lecture 4: Guanosine, Intron, Spliceosome

BISC 202 Chapter Notes -Histone Code, Repressor, Chromatin

BISC 202 Chapter 12: 12.2 Lessons from Yeast The GAL system.docx

Related Questions