Exam 4 Molecular Genetics Quizlet

How many promoters are in an operon?

1

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

A trans-acting factor

Catabolite activator protein binds to what site?

CAP site

Monod and Jacob studied lactose metabolism in __ ______.

E. Coli

T/F The CAP protein is an activator that binds to the operator.

False

T/F The structural proteins encoded by the lac operon are involved in lactose synthesis.

False

The enzyme beta-galactosidase cleaves the sugar lactose into ____________ and _______________ .

galactose ; glucose

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

short DNA segments

β-ONPG can be used to detect levels of β-galactosidase, because β-galactosidase cleaves β-ONPG into a substance with a ______ color.

yellow

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

False

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

False, The most common way that bacteria regulate gene expression is by influencing the rate of transcription initiation.

True or false: Gene regulation is constant.

False, because gene expression can vary under different conditions

The ______ gene encodes a repressor protein.

LacI

β-galactosidase activity can be detected using the lactose analog β- __________ because β-glalactosidase cleaves it to a product with a yellow color. (Use an abbreviation.)

ONPG

Repressor binds to what site?

Operator

How would the interpretation of the Jacob, Monod, and Pardee experimental results change if lacO was mutated instead of lacI?

The lac operon has constitutive expression and O has a cis-effect

RNA polymerase binds to what site?

The promoter

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

Trans-acting factor

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

a single promoter

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

The Lac repressor protein binds to the operator and ______.

blocks transcription

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

cis - acting

Unregulated genes have ______

constant levels of expression.

Unregulated genes are also called ___________________ genes.

constitutive

When glucose is present, __________.

cyclic AMP is low, CAP does not bind to the activator binding site, and transcription of the lactose operon is turned off

Monod, Jacob, and Pardee studied an E. coli strain with a lacI- mutation in which the lac operon was expressed ______.

even in the absence of lactose

The lacA gene encodes the enzyme _____________ ____________.

galactoside transacetlyase

In attenuation, transcription ______.

is stopped prematurely

Monod and Jacob studied __________ metabolism in E. coli

lactose

The lacA gene encodes galactoside transacetylase, an enzyme that covalently modifies ______.

lactose

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

merozygote

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

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

operon

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

promoter

The operon is flanked by a _____________ hat signals the beginning of transcription and a ____________ that signals the end of transcription.

promoter ; terminator

An RNA molecule that can exist in two different secondary conformations and thereby affect gene regulation is known as a(n) _________ .

riboswitch

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 is regulating.

Which of the following sets of conditions would result in high levels of gene transcription from the lac operon?

Low glucose, high lactose

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

Merozygote

The lacY gene encodes lactose ____________ , a membrane protein.

permease

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

polycistronic

The enzyme β-galactosidase is encoded by which gene?

LacZ

How does an effector molecule influence gene expression?

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

T/F CAP binding causes the DNA to bend facilitating RNA polymerase binding.

True

T/F The lacI gene makes a repressor protein.

True

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

cannot transcribe

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

increase

In the lac operon, the CAP site is located next to the __________. When both lactose and glucose are present, this leads to a rate of transcription that is __________.

promoter; low

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

repressor

An inducer could bind to a(n) ______ and prevent it from binding to the DNA, or it could bind to a(n) ______ and cause it to bind to the DNA.

repressor; activator

The conversion of a riboswitch form one conformation to another is due to ______.

the binding of a small molecule

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

the rate of transcription initiation

The product of the lacY gene is required for ______.

the transport of lactose into the bacterial cell

Jacob, Monod, and Pardee isolated bacteria with mutations that resulted in the constitutive expression of the ______________ operon even in the absence of lactose.

lac

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

three

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

True

You identify a strain of bacteria that has a mutated trp operator that cannot bind the repressor. Under what circumstances will the trp operator be transcribed?

The trp operon will be transcribed when levels of tryptophan are in the cell are low.

T/F The product of lacI is an allosteric protein that can undergo a conformational change when allolactose binds to it.

True

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

activator

A polycistronic mRNA contains the sequence(s) ______.

of two or more genes