BIOL 400 Ch 14 LearnSmart

Which two of the following statements about the interaction between the lac repressor and inducer are true?

- Inducer binding changes the repressor shape. - Inducer binding causes repressor to lose ability to bind to the operator sites

At which of the following operator sites must the lac repressor bind to ensure transcription inhibition?

01

Order the following events in the regulation of the trp operon of E. coli when there is little charged tRNA-Trp present in the cell.

1. RNA polymerase initiates transcription at the promoter 2. A ribosome initiates translation of the trpL gene 3. The ribosome stalls in need of charged tRNA-Trp 4. The antiterminator loop forms in the transcript 5. RNA polymerase transcribes the structural genes of the trp operon

Order the following events in the regulation of the trp operon of E. coli when charged tRNA-Trp is abundant in the cell.

1. RNA polymerase initiates transcription at the promoter 2. A ribosome initiates translation of the trpL gene 3. the trpL peptide is synthesized efficiently 4. the terminator loop forms in the transcript 5. RNA polymerase falls off the template 5. Translation terminates at the UGA stop codon

When lactose catabolism is not required, the lac repressor binds to one of ________ different lac operators.

3

When lactose catabolism is not required, the lac repressor binds to one of ____________ different Lac operators

3

The signaling molecule used in quorum sensing by Vibrio fischeri and many other Gram-negative bacteria is ____.

AHL

The adenyl cyclase enzyme converts _____ to cAMP and PPi.

ATP

Which of the following is the inducer of the lac operon?

Allolactose

The Lac repressor binds to the lac operon at the position(s) indicated by the letter _____.

B only

ATP is converted to cAMP by the enzyme ______ _______

Blank 1: adenyl, adenylyl, or adenylate Blank 2: cyclase

As a general rule, Gram-negative bacteria use riboswitches to regulate the _________ of mRNA, and Gram-positive bacteria use riboswitches to regulate _______ termination

Blank 1: translation Blank 2: transcriptional or transcription

In E.coli regulatory pathways, which molecule functions to ensure that glucose is used as the preferred carbon and energy source?

CAP

Which statement best describes the result of CAP binding to the CAP recognition site?

CAP bends the DNA within two helical turns

The transcription of all catabolite operons are regulated by which two of the following?

Regulatory protein specific to the operon Catabolite activator protein

Which two of the following describe the catabolite activator protein?

Represses specific operons when glucose is available Activates specific operons when glucose is not available

Transcription of the trp operon is controlled by which two of the following mechanisms?

Repressor protein inhibits initiation Premature termination through attenuation

Which two of the following are mechanisms that can control transcription of the trp operon by way of the attenuator region?

Ribosome translates at normal rate due to adequate tryptophan levels - pause and terminator loops are formed Ribosome stalls in region 1 due to low tryptophan levels - antiterminator loop forms

Which condition is most likely to NOT result in attenuation of transcription of the trp operon?

Slow ribosome activity due to low tryptophan levels

Which three of the following are components of a bacterial operon?

Structural genes Operator Promoter

In the image of a diauxic growth curve, at time 3 hours, which of the following is true?

The lac operon is repressed.

In the regulation of the trp operon of E. coli, when translation does not occur, which of the following happens?

The pause and terminator loops form and transcription stops before RNA polymerase reaches the structural genes of the operon.

A(n) _______protein is a DNA-binding protein that promotes transcription initiation.

activator

When _____ proteins bind to their transcriptional regulatory sites they facilitate the binding of RNA polymerase.

activator

Proteins that promote transcription initiation by binding to DNA are called ____.

activator proteins

The enzyme β-galactosidase converts lactose to ____________

allolactose

The sugar ____________ is the inducer of the lac operon.

allolactose

Binding of an effector to one domain of a transcriptional regulatory protein changes the conformation of its DNA-binding domain. This is an example of _____.

allosteric control

Quorum sensing is used by Vibrio fischeri to control _______.

bioluminescence

This image shows the molecules involved in transcriptional regulation of the lac operon. Considering the lac repressor and CAP proteins illustrated here, which carbon sources are available?

both lactose and glucose

Which cyclic nucleotide activates CAP?

cAMP

The global control of operons encoding enzymes for the catabolism of carbohydrates that must be modified prior to entering glycolysis is referred to as ____.

catabolite repression

Genes that are expressed continuously are called ____.

constitutive genes

Aporepressors are activated by the binding of a(n) ____.

corepressor

Aporepressors are synthesized in an inactive form and are activated by the binding of small effector molecules called ____________

corepressors or co-repressors

For most transcriptional riboswitches, there are two configurations of the leader of an mRNA. What determines the configuration of the leader region?

effector binding to the mRNA

Regulation of transcription initiation for the trp operon is accomplished at two levels, 1: transcription initiation by the trp repressor and 2: transcription __________ by the process called attenuation.

elongation

The level of some enzymes, such as β-galactosidase, increase significantly in the presence of a small effector molecule called a(n) .

inducer

Small effector molecules whose presence increases the level of specific enzymes are called ____.

inducers

______ genes encode enzymes whose level is increased by the presence of small effector molecules.

inducible

Enzymes whose level increases in the presence of small effector molecules are encoded by ____.

inducible genes

Which two proteins are regulators of the lac operon?

lac repressor Catabolite activator protein

In this image of the trp operon, the repressor protein, indicated by the letter R, binds to the DNA at the _____ site.

operator

The mechanism to synthesize cAMP when glucose is absent involves the system for _____.

phosphorylating glucose as it enters the cell

DNA-bound repressor proteins inhibit the initiation of transcription by either ____.

preventing the movement of RNA polymerase blocking the binding of RNA polymerase

When CAP protein binds to the CAP _________ site of a catabolite operon, it causes a bend in the DNA which stimulates transcription.

recognition or binding

Genes that are expressed only when the enzymes they encode are needed are said to be ____.

regulated

The nucleotide sequence that encodes the leader sequence of the trp operon is ____.

trpL

Which two of the following statements about the inhibition of transcription by the lac repressor protein are true?

Binds to O1 and one additional lac operator site Bends the DNA in the promoter region

The binding of __________ to the catabolite activator protein causes it to change to the active form.

Blank 1: cAMP, cyclic adenosine monophosphate, cyclic AMP, or cyclic-AMP

The lac operon is under the regulatory control of the lac repressor protein, and the _________ ________ protein or CAP.

Blank 1: catabolite Blank 2: activator

The positive regulatory system called ________ __________ prevents the expression of genes encoding proteins necessary for the utilization of sugars other than glucose when adequate supplies of glucose are present.

Blank 1: catabolite Blank 2: repression

Full transcriptional activation of the lac operon requires high levels of the sugar _________ and low levels or the absence of the sugar _______

Blank 1: lactose Blank 2: glucose

Vibrio fischeri uses quorum sensing to control the production of ________

Blank 1: light, bioluminescence, or luciferase

AHL is synthesized by the enzyme AHL synthase, encoded by the gene ____________

Blank 1: lux1 or luxI

In E. coli, the proteins necessary to utilize lactose as an energy and carbon source will not be expressed, even when lactose is present, unless the _________ __________ protein is activated by the absence of glucose in the cell.

Catabolite activator

Match the following concerning types of genes. Constitutive genes Regulated genes

Constituted Genes : Gene that are continuously expressed Regulated genes: Genes that are only expressed when needed

______ genes are continuously expressed.

Constitutive

Which of the following is NOT a component of bacterial operons?

Enhancer

True or false: The trp operon is an example of a positive control system.

False

Gram-positive bacteria: Gram-negative bacteria:

Gram-positive bacteria: Control of transcription Gram-negative bacteria: Control of translation

Which two of the following conditions must exist to fully induce the lac operon?

Lack of preferred carbon and energy source Lactose present in the medium

Which two of the following conditions are required for full activation of the lac operon?

Low levels or absence of glucose Presence of lactose

The trp operon is best described as an example of the ______.

Negative transcriptional control of repressible genes

Which statement about the trp operon is true?

Operon is functional when tryptophan is absent.

In the regulation of the trp operon of E. coli, when translation does not occur, the pause and terminator loops form and transcription stops before ____ reaches the structural genes of the operon.

RNA polymerase

In the context of transcriptional regulatory proteins, allosteric control refers to _____.

an effector binding in one domain changing the conformation of another domain

A regulatory process that results in transcription termination within a leader sequence that precedes the structural genes is termed ___________

attenuation

Termination of transcription elongation before RNA polymerase enters the first structural gene of an operon is called ____.

attenuation

DNA-bound activator proteins promote transcription initiation by ____.

facilitating RNA polymerase binding

The catabolite activator protein functions in a regulatory network that allows E. coli to preferentially use ___________ over all other carbon and energy sources.

glucose

The catabolite activator protein functions in a regulatory network that allows E. coli to preferentially use ____________ over all other carbon and energy sources.

glucose

The binding of inducer to the lac repressor protein does NOT result in which of the following?

lac repressor binds to operator

In this image of the lac operon, the structural genes are _____.

lacZ, lacY, and lacA

The lac operon is expressed at high levels when the sugar ___________ is available and a preferred source of carbon and energy is lacking.

lactose

When _________ is present in the environment, it is transported into E. coli cells by lactose permease.

lactose

This image shows the molecules involved in transcriptional regulation of the lac operon. With the lac repressor and CAP proteins illustrated here, which carbon sources are available?

lactose but no glucose

Proteins that are responsible for the induction or repression of enzyme encoding genes are referred to as ______ proteins

regulatory

Proteins involved in the control of gene expression in processes such as induction and repression are referred to as ____.

regulatory proteins

______ genes encode enzymes that have their expression levels decreased by the presence of pathway products.

repressible

The genes that encode enzymes that have their expression levels decrease in the presence of pathway end-products are best described as ____.

repressible genes

A(n) ________ protein is a DNA-binding protein that inhibits transcription initiation.

repressor

When ______ proteins bind to the operator they block the binding of RNA polymerase or inhibit its movement.

repressor

Transcription of the trp operon is regulated at the level of initiation by the trp repressor, and at the level of elongation by a process called _________

attenuation

Transcription initiation of the trp operon is regulated by both ____.

attenuation trp repressor

The trpL operon encodes the leader peptide and _______ sequences.

attenuator

The lac repressor protein inhibits transcription by ____.

bending DNA in the promoter region

Lactose is transported into the E. coli cell by ____.

lactose permease

The trpL operon encodes the _______peptide and attenuator sequences.

leader

For most transcriptional riboswitches, there are two configurations of the mRNA leader region. The configuration is determined by effector binding to the _____.

mRNA leader

Bacterial repressor proteins bind to a DNA sequence called the __________

operator

In bacteria, repressor proteins bind to a specific DNA sequence called the ____.

operator

In the trp operon of E. coli, when charged tRNA-Trp is abundant in the cell, the terminator loop forms in the transcript because _____.

the ribosome follows RNA polymerase and efficiently synthesizes the TrpL peptide

In the trp operon of E. coli, when there is little charged tRNA-Trp present in the cell, the antiterminator loop forms in the transcript because _____.

the ribosome stalls but the RNA polymerase keeps moving along the transcript

True or false: The intracellular level of cAMP depends on the state of a protein that functions in the phosphoenolpyruvate:sugar phosphotransferase system (PTS).

true

In this image of the trp operon, the repressor protein is indicated by the letter R. What is the co-repressor molecule (circled) needed for the repressor protein to be able to bind to DNA?

tryptophan

The trp operon is only active when _________ is not present in the cell.

tryptophan

Lactose is converted to allolactose in the E. coli cell by ____.

β-galactosidase

Proteins that inhibit transcription initiation by binding to DNA are called _____.

repressor proteins

True or false: All catabolite operons are regulated by CAP and a regulatory protein that is specific to each operon.

true