BIOL 22100 Lecture Notes - Lecture 16: Gene Expression, Repressor, Operon

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26 Aug 2016

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I is the repressor and the pozy genes are all part of the lac operon. Po are part of the regulatory region and zya are part of the structural genes multiple genes are made as one mrna from a single control region. Each gene in the operon has its own shine-dalgarno sequence. Repressor- promoter operator b-galactosidase permease transacetylase = i-pozya (in order) The repressor protein can bind downstream from the promoter. Where it binds is called the operator (o) The activator protein binds upstream of the promoter to allow mrna synthesis. This is simply referred to the activator binding site. This can help if the promoter doesn"t match the consensus to well as it can stabilize it. An environmental signal that can turn a gene on is called an inducer. It works by binding to the repressor protein to inactivate it so the rna polymerase+sigma factor can resume transcription.

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?

In the following points, I have summarized Lac operon in Ecoli. I need to check if this is on the right track? and where does 'cleavage of disaccharides' fit into this picture?

Lactose is a disaccharide and the bacteria need specific genes to manage catabolism

1) The lacl promotor gene synthesis the repressor protein which binds to the operator gene stopping the RNA polymerase from coding the lac operon genes

2)But when lactose is present, it needs the specific genes to catabolise lactose

3) So, When allolactose (a derivative of lactose)is present, it binds to the repressor protein, the repressor releases from the operator gene

4) This allows the RNA polymerase can attach to the DNA control region

5) And drive down the operon for transcription and induction of the enzyme lacZ(beta-galactosidase) lacY and lacA which breaks lactose down into glucose and galactose

6) When the lactose is all gone, the repressor returns to the operator in a feedback loop system

A theoretical operon (amo) in E. coli contains several structural genes encoding enzymes involved in the biosynthesis of a particular amino acid. Unlike the lac operon, in which the repressor gene is separate from the operon itself, for the amo operon, the repressor gene is found within the operon itself. When the end product amino acid is present, it binds to the repressor, and this complex binds to the operator, repressing the operon. In the absence of the amino acid, the repressor fails to bind to the operator, and transcription proceeds. Characterize this operon, comparing it to the regulation of the lac and trp operons. Be sure to discuss how regulation is affected by having the repressor gene as part of the operon.

Then, consider the following mutations:

a) Mutation in the operator region;

b) Mutation in the promoter region;

c) Mutation in the repressor gene.

In each case, state whether the operon will be transcribed or not, and describe how the mutation affects the regulation of the operon. Compare each response to the equivalent situation in the lac and trp operons.

BIOL 22100 Lecture Notes - Lecture 16: Gene Expression, Repressor, Operon

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