Chapter 16 Practice Quiz

How many promoters are in an operon?

1

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

1

What stem-loop conformations favor attenuation in thetrp operon?

3-4

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

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.

In Jacob, Monod, and Pardee's experiment, what would have been the conclusion if all four tubes produced a yellow color when β-ONPG was added?

Expression of the lac operon is constitutive whether lacI is functional or not

A mutation in the lacI gene prevents the gene product from binding allolactose. What will the expression level of the operon be in the absence of lactose?

No transcription

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

Phosphorylation of an enzyme

A deletion in an operon removes the terminator. How will that affect the transcript that is produced from the operon?

The transcript will be produced, but longer than normal

A deletion in an operon removes the promoter. How will that affect the transcript that is produced from the operon?

The transcript will not be produced

If the Trp codons in thetrpL gene were mutated to encode another amino acid, what would the result be?

The trp operon would never be transcribed.

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.

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 a complementary RNA and prevents its translation

Because it stabilizes mRNA, antisense RNA enhances translation.

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

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 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 affect regulation of ______.

transcription and translation

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

trpL

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

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

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

In a particular E. coli strain, a mutation in the thiMD operon results in improper formation of the stem loop secondary structure making it impossible to bind TPP. There are two enzymes encoded by the thiMD operon. How many of the enzymes encoded in the thiMD operon are translated?

two