BSCI 1001 Study Guide - Quiz Guide: Lac Operon, Trp Operon, Rna Splicing

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maroonhedgehog882

3 Aug 2016

School

Vanderbilt University

Department

Biological Sciences

Course

BSCI 1001

Professor

Phillips Shawn

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Discuss the two types of operons that express negative gene regulation and explain how they work the two types of operons are repressible and inducible operons. The trp operon is an example of a repressible operon because its transcription is usually on but it can be inhibited when tryptophan binds allosterically to a regulatory protein. An example of an inducible operon is the lac operon. In contrast to the repressible operons, an inducible operon is usually off but it can be stimulated when a specific small molecule interacts with a regulatory protein. So in the case of the lac operon, when lactose is present, then the repressor is inactive and the operon is on. In general, describe what is the effect of histone acetylation and dna methylation on gene expression the acetylation of histone tails promotes loose chromatin structure that permits transcription.

Related Questions

What is an operon?

What is the evolutionary advantage of an operon?

What is the difference between a repressible operon and an inducible operon?

Describe the state of the corepressor for a trp operon that is not expressing the operon gene and a lac operon that is not expressing the operon gene.

What is cell differentiation?

Name three different levels of gene regulation in a multicellular eukaryotic organism.

What is gene regulation at the chromatin level? Give one example of how it can be carried out.

Control elements are a form of gene regulation found at what level of gene regulation?

Are there forms of RNA that can block translation? If so give an example.

What do master regulatory genes have to do with control elements?

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)

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?

BSCI 1001 Study Guide - Quiz Guide: Lac Operon, Trp Operon, Rna Splicing

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