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
