Genetics Ch. 16

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The term enzyme adaptation is used to describe an enzyme that appears in a living cell following exposure to a specific substrate.

True

cAMP is a small effector molecule.

True

How many promoters are in an operon?

1

In Jacob, Monod, and Pardee's experiment, how many functional copies of lacl were there in the merozygote?

1

What stem-loop conformations favor attenuation?

1-2 and 3-4

For these questions, match the following to its appropriate letter. Use each letter only once. 1) Cis-mutation 2) Trans-mutation 3) Inducer 4) Corepressor 5) Repressible 6) Inducible

5) Trp operon 3) Allolactose 1) Operator 6) Lac operon 2) Lacl 4) Tryptophan

Regulation of gene expression may occur at which of the following levels?

All of the answers are correct.

Which of the following encode polycistronic mRNA?

All of the answers are correct.

Which of the following is found in an operon?

All of the answers are correct.

What would be the result if the U-rich sequence after the fourth stem loop in the trp operon was replaced by a UG-rich sequence?

Attenuation would not occur if tryptophan was high.

In the Jacob Monod merozygote experiment, what was indicated by the presence of a yellow color when b-ONPG was added?

Beta-galactosidase was present.

Because it stabilizes mRNA, antisense RNA enhances translation.

False

DNA that contains instructions for two or more structural genes produces monocistronic mRNA.

False

In the lac operon, the operator is an example of a trans-effect genetic regulation.

False

In the lac operon, the operator site is recognized by an activator protein.

False

Negative transcriptional regulation is conducted by activator proteins.

False

Operons that code for anabolic enzyme systems are typically regulated by inducers.

False

Operons that code for catabolic enzyme systems are typically regulated by repressors.

False

If CAP could not bind to its CAP site, then what would be the result? Assume lactose is present in each scenario.

Transcription would be difficult to activate in the absence of glucose.

A riboswitch is an RNA molecule that can exist in two different conformations. Conversion from one to another is due to the binding of a small molecule to the riboswitch.

True

Constitutive genes are those that have constant levels of expression.

True

Coupled transcription and translation occur under conditions in which the tryptophan concentration is very low.

True

In the E. coli riboswitch, mRNA gets translated when TPP is low.

True

In the trp operon, tryptophan is a corepressor.

True

Repressor proteins are responsible for negative transcriptional regulation.

True

The form of regulation that involves a physical change in the shape of an enzyme is called allosteric regulation.

True

Allosteric regulation is accomplished by

a small molecule that fits into a site on the enzyme that is not the active site.

Antisense RNA does which of the following?

binds to the mRNA and prevents translation.

Which of the following is not associated with positive transcriptional regulation?

corepressors

Enzymes involved in metabolism are most likely regulated via ________.

feedback inhibition

If a bacterium is placed in an environment that contains both glucose and lactose, the regulation of the lac-operon will allow which nutrient to be processed first?

glucose

Translational regulatory proteins recognize specific areas of what molecule?

mRNA

The lac operon is under what type of control?

negative control

Which of the following is not an example of translational regulation in prokaryotes?

phosphorylation of an enzyme

The regulation of protein function, not gene-expression is called ______ regulation.

posttranslational

A gene is inducible and under negative control. Which of the following pairs will allow expression of this gene?

repressor + inducer

CAP affects which operon(s)?

the lac operon

Riboswitches have been shown to have regulation of ___________?

transcription and translation

What is the gene responsible for attenuation in the trp operon?

trpL


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