Chapter 16 SB Gene Regulation in Bacteria

Transcription regulation by an activator protein is considered to be ______ control.

Positive

How does an effector molecule influence gene expression?

The effector molecule binds to a regulatory protein and affects its ability to bind DNA.

Why is transcription of the lac operon low when both lactose and glucose are present?

The low levels of cAMP result in CAP not binding to the CAP site.

The three protein-encoding genes in the lac operon are _, _, and _.

lacZ, lacY, lacA

In postranslational regulation, the final product of a metabolic pathway may bind to the _ site of an enzyme and inhibit its catalytic ability.

regulatory

The mRNA made from the ______ gene contains codons for 14 amino acids that form the trp leader peptide.

trpL

In the trpL mRNA, the number of stem-loops that are possible is_

3

The lac repressor is composed of how many identical subunits?

4

Multiple Choice Question What is a riboswitch?

A region within an mRNA that regulates the translation of the mRNA of which they are a part

Effector molecules influence gene expression by binding to DNA. True/False

False

Gene expression is always the same. True/False

False

On a regulatory protein, an allosteric site is the same as the active site. True/False

Fase

Can a particular segment of mRNA from the trp operon participate in the formation of more than one stem loop at the same time?

No

What type of regulator does not need to be adjacent to the gene(s) it is regulating?

Trans-acting factor

A benefit of gene regulation is that encoded proteins may not be produced when they are not needed. True/False

True

What type of regulator does not need to be adjacent to the gene(s) it is regulating?

What type of regulator does not need to be adjacent to the gene(s) it is regulating?

An operon is a group of two or more genes under the transcriptional control of ______.

a single promoter

Which types of posttranslational covalent modifications are typically reversible?

acetylation, phosphorylation, methylation

A regulatory protein that binds to DNA and increases the rate of transcription is a(n) ______.

activator

The transport of glucose into a bacterial cell causes the intracellular level of cyclic-AMP to fall because the enzyme _ _

adenyl cyclase

The transport of glucose into a bacterial cell causes the intracellular level of cyclic-AMP to fall because the enzyme _ is inhibited.

adenyl cyclase

Cyclic-AMP is a small effector molecule produced by the enzyme

adenylyl cyclase

Constitutive genes encode proteins that the cell needs ______.

all the time

The small effector molecule that prevents the lac repressor from binding to the operator site is_

allolactose

A regulatory site on a protein where an effector molecule binds is called a _ site.

allosteric

An enzyme may contain two sites: a catalytic site, and a regulatory or _ site.

allosteric

In the absence of lactose, the lac repressor ______.

allows very small amounts of lac operon enzymes to be made

The binding of a small effector molecule to a regulatory protein alters the regulatory protein's conformation, and that ______.

alters the protein's ability to bind to DNA

What do you call an RNA strand that is complementary to an mRNA molecule?

antisense RNA

Constitutive genes ______.

are unregulated

Regulation of the trp operon involves the process of _, in which transcription begins but terminates before the entire mRNA is made.

attenuation

The trp operon is regulated by a repressor protein and by _ in which transcription is stopped prematurely.

attenuation

Riboswitches may be found in ______.

bacteria, archaea, algae fungi, and plants

When tryptophan levels are high, tryptophan binds to trp repressor protein causing a conformational change that in turn causes the trp repressor to ______.

bind to the operator site

The lac repressor protein binds to the operator and ______.

blocks transcription

During attenuation, transcription begins ______.

but is terminated before the entire mRNA is made

The small effector molecule produced by the enzyme adenylyl cyclase is ______.

cAMP

When the lac repressor is bound to the operator, RNA polymerase ______ the lacZ, lacY, or lacA genes.

cannot transcribe

Inducible operons usually encode ______ enzymes, and repressible operons usually encode ______ enzymes.

catabolic; anabolic

The somewhat imprecise term that describes how transcriptional regulation is influenced by glucose is _ _

catabolite repression

A DNA segment that must be adjacent to the gene(s) it regulates is a _ _ element

cis acting

Antisense RNA is an RNA strand that is _ to an mRNA molecule.

complementary

Unregulated genes have ______.

constant levels of expression

For the trp operon, tryptophan acts as a ______.

corepressor

The binding of the lac repressor to the operator shuts down transcription from the lac operon when lactose is ______ the environment.

depleted from

Osmotic shock or heat shock are examples of_stress that might require a bacterium to produce a specific protein.

environmental

The genes in the trp operon encode ______.

enzymes used in tryptophan biosynthesis

The mRNA made from the trpL gene has four regions that can ______.

form stem-loops

The lac repressor functions as a homotetramer, a protein composed of ______ subunits.

four identical

In catabolite repression, transcription is influenced by the presence of ______.

glucose

The transport of_ into a cell causes a_ in the concentration of cyclic-AMP by inhibiting adenylate cyclase.

glucose; decrease

An inducer is a small effector molecule that causes the rate of transcription to ______.

increase

In feedback inhibition, the final product in a metabolic pathway ______.

inhibits an enzyme that acts early in the pathway

In attenuation, transcription ______.

is stopped prematurely

The ______ gene encodes a repressor protein.

lacI

When only ______ is present in bacterial cells, cAMP levels are high.

lactose

When both lactose and glucose are absent from bacterial cells, concentrations of cAMP are ______.

low

When both lactose and glucose are present, transcription of the lac operon is ______.

low

When tryptophan levels in the cell are_ the trp repressor cannot bind to the_site. This allows RNA polymerase to transcribe the genes required for the synthesis of _.

low operator tryptophan

When the lac repressor binds to the lac _ site, RNA polymerase cannot transcribe the lacZ, lacY or lacA genes.

operator

A group of two or more genes under the transcriptional control of a single promoter is called a _.

operon

An operon encodes a _ mRNA, an RNA that contains the sequences of two or more genes.

polycistronic

Control of proteins already present in the cell is called _ regulation.

posttranslational

Proteolytic processing, formation of disulfide bonds, and addition of prosthetic groups are all types of ______.

posttranslational covalent modification

Allolactose is a small effector molecule that binds to the lac repressor and ______.

prevents the repressor from binding to DNA

In an operon, the ______ signals the beginning of transcription.

promoter

The operon is flanked by a sequence called a _ that signals the beginning of transcription and one termed a _ that signals the end of transcription.

promoter, terminator

When attenuation occurs in the trp operon, the mRNA is ______.

terminated before transcription of the genes required for tryptophan biosynthesis

The mRNA made from the trpL gene contains codons for 14 amino acids that form ______.

the trp leader peptide

When attenuation occurs, the mRNA from the trp operon is made as a short piece that terminates shortly past the ______ gene.

trpL

A polycistronic mRNA contains the sequence(s) for ______.

two or more genes

Which genes in the trp operon encode enzymes involved in tryptophan biosynthesis? trpC trpE trpB trpA trpD

CEBAD

The binding of ______ to the lac repressor promotes a conformational change that prevents the repressor from binding to the lac operator.

allolactose

The intracellular concentration of the inducer _ remains high as long as lactose is available in the environment.

allolactose

Unregulated genes are also called_genes.

constitutive

Post translational regulation refers to ______.

control of proteins already in the cell

In bacteria, the most common way to regulate gene expression is by influencing the ______.

rate of transcription initiation

The phenomenon in which the level of gene expression can vary under different conditions is gene_

regulation

A regulatory protein that binds to DNA and inhibits transcription is called a_

repressor

An element within an mRNA that can bind a ligand and switch the mRNA to a different secondary conformation is a_

riboswitch

Regulatory RNA sequences known as _ are widespread in nature and may be found in bacteria, archaea, algae, fungi, and plants.

riboswitch

The CAP site and the operator site are ______ that function in gene regulation.

short DNA segments

The mRNA from the trpL gene has four regions that are complementary to each other and cause the mRNA to form _-_.

stem-loops