BIOL 2030 Lecture Notes - Lecture 7: Catabolism, Operon, Arabinose

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salmonrat522

12 Apr 2016

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Lecture 7: four geneic systems for the control of prokaryoic operons. When there are two sets of genes in an organism (the second set is typically in the form of a plasmid) This means that there are two operons and the products from both can interact with each other. Allows for experiments to put a variety of diferent combinaions of mutants and non- mutants together. Diference: inducible the signal molecule is present and that induces the synthesis of the enzyme needed for its breakdown (typically catabolic pathways) Example: lactose operon: repressible the signal molecule is present and that represses the synthesis ot the enzyme needed for its producion (typically anabolic pathways) Negaive control: under control by a repressor, the repressor will turn of producion. Posiive control: the signal molecule will acivate the regulatory protein which will help rna polymerase bind and encourage transcripion, example: arabinose operon (negaive control)

Related Questions

Below are possible alleles found in the lac operon.

Repressor gene:

I^s (superrepressor; can't bind allolactose, but can bind operator)

I⁺ (inducible; wild-type)

I^- (constitutive; can bind allolactose, but can't bind operator)

Operator:

O^c (constitutive; can't bind repressor)

O⁺ (inducible; wild-type)

A. Which of the following combinations below will not express Î²-galactosidase even when lactose is present? Circle and explain your answer.

I⁺O⁺

I^-O^c

I^sO^c

I^sO⁺

I^-O⁺

B. Which of the following combinations below will express Î²-galactosidase only if lactose is present? Circle and explain your answer.

I⁺O⁺

I^-O^c

I^sO^c

I^sO⁺

I^-O⁺

Note: This question is for an INTRODUCTORY genetics class, so please try to answer in a way that an INTRODUCTORY student would be able to understand.

silverdinosaur935

3. Assume that in a bacterial species you discover a cluster ofthree genes (A, B, and C) that accountfor the enzymatic production of a cellulose-like carbohydrate (clc)that is needed as a component of its cell wall. When there issufficient clc is in the cell, the three enzymes are notsynthesized. However, when more clc is needed, the three enzymesare abundantly produced. This cluster of genes appears to be undercoordinate control because deletion of a distant gene (R)results in constitutive expression of all three genes even whenexcess clc is present. When mutations (P^-) occur in a region upstream ofgene A, no synthesis of the three enzymes occurs even whenclc levels are extremely low. Mutations (O ^-)that occur right next to the P ^- mutationsresult in constitutive expression of all three genes even when clcis present at high levels.

(a) Do the three genes (A, B,and C) behave as if they were part of an operon?

(b) What type of control (positive or negative)seems likely to control the production of the three enzymes?

(c) What is the most likely function of theprotein produced from gene R?

(d) Do you expect that clc is an inducer,inhibitor, or corepressor?

(e) You discover that clc binds to the proteinmade from gene R. What is the most likely effect of this binding?(Hint: will it cause the R protein to bind DNA or fall off ofthe DNA?)

(f) Where do you think protein R binds?(Hint: P region or O region ?)

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BIOL 2030 Lecture Notes - Lecture 7: Catabolism, Operon, Arabinose

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