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
