BSCI 222 Study Guide - Midterm Guide: Repressor, Operon

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limebee726

1 Oct 2015

School

University of Maryland

Department

Biological Sciences Program

Course

BSCI 222

Professor

Dr.Straney

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Document Summary

Gss worksheet: briefly explain the difference between a positively and a negatively controlled operon, as well as an inducible and repressible operon. Draw the mechanism by which a negative inducible and a positive repressible operon control transcription. If the regulatory protein that binds to the operator is an enhancer, the operon is under positive control. If the regulatory protein is a repressor, the operon is under negative control. If transcription is usually off (i. e. not occurring under normal conditions), and something must occur for it to be induced (i. e. turned on), the operon is inducible. On the contrary, a repressible operon is usually on, and something must occur for it to be turned off. For part two of the question, refer to figure 16. 6 on page 439 of the textbook for a simple diagram of transcription regulation in both cases: fill in the following table. Use a (+) sign to indicate the synthesis of.

Related Questions

Dr. Pollution and his friends have cloned and sequenced an operon that is required for the breakdown of the common soil pollutant trichloroethylene (TCE). They find that this operon is expressed when TCE is present, and is not expressed when TCE is absent. Dr. Pollution says âAha! The operon must be under positive control and an activator protein must exist! Letâs find it.â Dr. Pollutionâs friends, however, say that the operon may be under either positive control (an activator protein) or negative control (repressor protein). (A) Explain why Dr. Pollutionâs friends are right. (B) Assume that in further experiments, they find that the TCE operon is under negative control. What would happen to regulation of the operon if the region where the regulatory protein binds is deleted?

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 222 Study Guide - Midterm Guide: Repressor, Operon

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