chapter 14 molec

In the trpL gene, which stem-loop together with the U-rich attenuator sequence acts as an intrinsic terminator?

3-4

Why is a merozygote better at complementing a mutation in a trans-acting factor than in a cis-acting element?

A cis-acting element must be adjacent to the gene it's regulating

Would using a merozygote better indicate regulation of a gene by a trans-acting factor or a cis-acting element?

A trans-acting factor

What happens when levels of allolactose rise inside an E. coli cell?

Allolactose binds to the lac repressor and prevents it from binding to the operator.

When only lactose is present in bacterial cells, levels of the effector molecules __ and __ are high.

Allolactose, cAMP

Who discovered attenuation by studying the trp operon?

Charles Yanofsky

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

Cis-acting element

What type of genes encode proteins the bacterial cell needs all the time?

Constitutive genes

The sequential use of sugars by a bacterial cell is called

Diauxic growth

True or false: Effector molecules influence gene expression by binding to DNA.

False

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

Glucose; decrease

The ______ gene encodes a repressor protein.

LacI

The enzyme β-galactosidase is encoded by which gene?

LacZ

What is the name for a strain of bacteria containing an F' factor?

Merozygote

The lacY gene encodes lactose __ , a membrane protein.

Permease

True or false: The lac repressor does not completely inhibit transcription of the lacZ, lacY, and lacA genes.

True

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

a single promoter

A regulatory protein that increases the rate of transcription is a(n)

activator

When bound to operator, the lac repressor ______.

allows very small amounts of the lac enzymes to be made

Constitutive genes ______.

are unregulated.

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

attenuation

Transcription begins but terminates before the entire mRNA is made during

attenuation

The Lac repressor protein binds to the operator and ______.

blocks transcription

Many bacterial species use sugars sequentially. This is called ______.

diauxic growth

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

glucose

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

high

When lactose is depleted from the environment, the ______.

intracellular concentration of allolactose falls

It has been shown that the lac operon has three __ sites to which the lac repressor can bind.

operator

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

operator

A(n) __ is a group of two or more genes under the transcriptional control of a single promoter.

operon

The research of Jacob and Monod provided ______.

our initial understanding of gene regulation

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

promoter

The operon is flanked by a __ that signals the beginning of transcription and a __ that signals the end of transcription.

promoter, terminator

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

regulation

When four molecules of allolactose are bound to the lac repressor, the lac operon is induced, and RNA polymerase ______.

transcribes the operon

The product of the lacY gene is required for ______.

the transport of lactose into the bacterial cell

In the trpL mRNA, _____ stem-loops are possible.

three

Unregulated genes are also called

constitutive genes

True or false: Gene regulation is constant.

false

Studies indicate that the lac operon has ______ operator site(s) for the lac repressor.

Three

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

Trans-acting factor

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

cannot transcribe

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

catabolite, repression

Unregulated genes have ______

constant levels of expression.

The research of Monod and Jacob that led to the initial understanding of gene regulation stemmed from an interest in ______.

enzyme adaptation

The genes in the trp operon encode ______.

enzymes used in tryptophan biosynthesis

When four molecules of allolactose are bound to lac repressor, and repressor can no longer bind to operator, and RNA polymerase is free to transcribe the operon, the operon has been

induced

In attenuation, transcription ______.

is stopped prematurely

Transcription regulation by an activator protein is considered to be ___

positive control

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

prevents repressor from binding to DNA

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

Adenylyl cyclase

A conformational change that prevents the lac repressor from binding to the lac operator occurs when __ binds to the lac repressor.

Allolactose

True or false: The rate of transcription initiation rarely influences overall gene expression.

False

How does an effector molecule influence gene expression?

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

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

adenylyl cyclase

Constitutive genes encode proteins the cell needs ______.

all the time

Select all of the following that are protein-encoding genes in the lac operon.

lacZ lacY lacA

The three protein-encoding genes in the lac operon are

lacZ, lacY, lacA

A strain of bacteria containing F' factor genes is called a __ , or a partial diploid.

merozygote

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

polycistronic

A regulatory protein that binds to DNA and inhibits transcription is a(n)

repressor

As levels of allolactose increase within an E. coli cell, allolactose binds to the lac __ , promoting a conformational change that prevents binding to the __ site on the DNA.

repressor, operator

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

the rate of transcription initiation

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

The small effector molecule __ prevents the lac repressor from binding to the operator site.

allolactose

A protein such as a repressor that inhibits transcription is exerting ____ control of transcription.

negative

A polycistronic mRNA contains the sequence(s) ______.

of two or more genes

The enzyme beta-galactosidase cleaves the sugar lactose into

galactose, glucose