BICD 100 Lecture Notes - Lecture 7: Chromatin, Catabolism, Post-Translational Modification

17 views2 pages

browngnu790

14 Oct 2016

School

UCSD

Department

Biol/Genetics,Cellular & Develop

Course

BICD 100

Professor

Keefe Reuther

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

Document Summary

Prokaryotic gene regulation: bacteria control transcription when responding to environmental changes, can regulate production of enzymes by feedback inhibition/gene regulation, gene expression in bacteria controlled by operon model, bacteria can regulate enzyme production or enzyme activity. When repressor becomes active, binds to operator to stop transcription: clicker: proteins that regulate gene expression through operons (a) interact directly through physical contact with dna. 2 types of negative gene regulation: repressible operons: usually on; binding of repressor to operator stops transcription, inducible operons: usually off; inducer inactivates repressor and turns on transcription. When lactose present, allolactose binds to repressor to inactivate repressor, allowing genes to be transcribed to break down the lactose present: inducible operons: catabolic pathways, repressible operons: anabolic pathways. Eukaryotic gene expression regulated at many stages: chromatin remodeling, transcription at open chromatin, rna processing: introns usually removed, mrna stability: goes from nucleus to cytoplasm.

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. 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

Are my answers correct?

1. If a bacterium with a wildtype lac operon is grown in the presence of lactose, high levels of transcription result for a while, however, eventually transcription is again down-regulated. If, on the other hand, the sugar IPTG is present (instead of lactose), transcription levels are high and remain high. What function do IPTG and lactose share? How are they differently affected by the operon product?

Lactose and IPTG are both inducers of the Lac-Operon. Lactose is a substance that the enzyme will react with (substrate), which is split or cleaved by the Beta-galactosidase. When you add lactose expressions level of lac operon will increase but as lactose is used by the beta-galactosidase expression levels of lac operon will decrease.

IPTG is a chemical cannot be split or cleaved by beta-galactosidase. The expression level of lac operon will remain the same.

Or Lactose can be easily broken down but IPTG cannot be broken down. What does expressions level mean?

2. If a lacI - bacterium is grown in the presence of the sugar X-gal, a blue dye appears; however, the concentration of X-gal decreases over time. What has happened to the X-gal?

If a lacI - bacterium is grown in the presence of the sugar X-gal, the Lacl is mutant or the gene is damaged which alters the genetic message carried by that gene. The LacI gene produces the repressor protein which switches off the operon, but since it is damaged no repressor protein is produced and the operon is switched on. The Lacl is transcribed into beta-galactosidase (lactose) The enzyme beta-galactosidase (lactose) splits or separates the X-gal which will result in decreased concentration of X-gal with time.

3. If a wildtype bacterium is grown in the presence of the sugar X-gal, transcription of the polycistronic m-RNA does not occur. What is X-gal unable to do? Without adding lactose (or genetically modifying the bacteria), how could you fix this problem

X-gal cannot form lactose, the repressor remains off and beta-galactosidase is not formed. This can be fixed by adding IPTG which can switch on the operon

BICD 100 Lecture Notes - Lecture 7: Chromatin, Catabolism, Post-Translational Modification

Document Summary

Get access

Related Documents

BICD 100 Study Guide - Midterm Guide: Dna-Binding Domain, Epigenetics, Repressor

BICD 100 Lecture Notes - Lecture 7: Trp Operon, Lac Operon, Chromatin Remodeling

BICD 100 Lecture Notes - Lecture 12: Lac Operon, Gene Expression, Ionizing Radiation

Related Questions