BIOL 2301 Lecture Notes - Lecture 17: Lactose Permease, Lac Repressor, Adenylyl Cyclase

33 views15 pages

skybear452

9 Mar 2018

School

Northeastern University

Department

Biology

Course

BIOL 2301

Professor

Eric J.Stewart

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

Document Summary

How genes are turned off and on to produce specific cell types and to respond to changing environmental conditions. What genes are expressed in different nutrient conditions or other environmental conditions. How many times will the rna be translated. How long will the rna last before it is degraded. In prokaryotes, mrnas undergo coordinate gene regulation which means that genes are transcriptions turned on or off together as a unit. A set of genes transcribed together from one promoter is called an operon. In negative regulation, transcription takes place (on) until a repressor binds to the dna upstream and turns it off. In inducible transcription, the repressor binding protein keeps the transcription turned off. An inducer binds to the repressor making the repressor losing its binding with the dna and therefore, transcription is turned on. Many catabolic biosynthetic pathways are inducible in nature.

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.

scarletwombat949

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 wildtype (the DNA sequence most commonly found in nature) lac operon, transcription is severely down-regulated. A mutation in lacI that causes an early stop codon in the sequence (called a lacI - strain) results in an operon that has high levels of transcription of the polycistronic m-RNA. What type of regulatory protein is the LacI protein (hint: we covered this type of protein in lecture)?

The Lac regulatory protein is called a repressor. (is this correct)

2) 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? (need help with this question)

Lactose and IPTG affected by the operon are both inducers of the Lac-Operon. (is this correct)

3) What is âepigeneticsâ? What forms of gene regulation are usually involved in epigenetic control of a trait? Why do we have such a limited understanding of epigenetic processes? (need help with this question)

Epigenetics is the study of phenotype changes that do not change the DNA sequence. Genes can be turned on and off based on environment situations of past generations, (parents or even grandparents) were exposed. Examples of some environmental factors could be diet, stress, smoking, drinking alcohol, and diseases. Histone modification and methylation are usually involved in epigenetic control of a trait. (is this correct)

BIOL 2301 Lecture Notes - Lecture 17: Lactose Permease, Lac Repressor, Adenylyl Cyclase

Document Summary

Get access

Related Documents

BIOL 2301 Lecture Notes - Lecture 15: Lac Operon, Repressor, Operon

BIOL 2301 Lecture Notes - Lecture 17: Adenylyl Cyclase, Wild Type, Cyclic Adenosine Monophosphate

BIOL 2301 Lecture 10: Prokaryotic Gene Regulation

Related Questions