Exam 3 Genetics - Gene Regulation
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
During attenuation, transcription begins,
but it is terminated before the entire mRNA is made.
Inducible operons usually encode ______ enzymes, and repressible operons usually encode ______ enzymes.
catabolic; anabolic
n the thi operon in B. subtilis, when levels of TPP are high, the mRNA folds into a stem-loop structure that
causes attenuation.
The ______ gene encodes a repressor protein.
lacI
A translational repressor protein binds to
mRNA near the start codon.
When TPP levels are low, the mRNA of the E. coli thiMD operon forms a stem-loop structure that Multiple choice question.
makes the Shine-Dalgarno sequence available to the ribosome.
A strain of bacteria containing F' factor genes is called a ____ or a partial diploid.
merozygote
When lactose is depleted from the environment,
the intracellular concentration of allolactose falls.
In bacteria, the most common way to regulate gene expression is by influencing
the rate of transcription initiation.
Monod, Jacob, and Pardee learned about the lac operon using bacterial strains called merozygotes. Since lacI encodes a diffusible protein, in a merozygote, the gene on the _________ could supply the mutant cell with functional repressor protein.
F' factor
What is the name for a strain of bacteria containing an F' factor?
Merozygote
What type of regulation does not need to be adjacent to the gene(s) it is regulating?
Trans-acting factor
In which type of regulation do riboswitches control access to the Shine-Dalgarno sequence?
Translation
Enzyme adaptation refers to the observation that
a particular enzyme appears within a cell only after the cell has been exposed to the substrate for that enzyme.
The observation that a particular enzyme appears within a cell only after a cell has been exposed to the enzyme's substrate is called enzyme _________
adaptation
A conformational change that prevents the repressor from binding to the lac operator occurs when ___________ binds to the lac repressor.
allolactose
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
In the E. coli thiMD operon, the 5' end of the mRNA folds into a structure with a stem-loop called the Shine-Dalgarno , ________ that keeps the Shine-Dalgarno sequence accessible to the ribosome.
antisequestor
In the thi operon in B. subtilis, when levels of TPP are low, the 5' end of the mRNA forms a stem-loop structure called a(n) ________ that allows transcription to continue.
antiterminator
A DNA segment that must be adjacent to the gene(s) it regulates is a ______ - _________ element
cis-acting
The probability that allolactose will bind to the lac repressor depends on the allolactose ________ in the bacterial cell.
concentration/amount
Unregulated genes have ______
constant levels of expression.
Posttranslational regulation refers to
control of proteins already in the cell
The binding of the lac repressor to the operator shuts down transcription from the lac operon when lactose is
depleted from the environment.
The normal lacI gene on the F' factor could rescue the lacI-mutants because the product of the lacI gene encodes a _____
diffusible protein.
The genes in the trp operon encode
enzymes used in tryptophan biosynthesis.
True or false: Gene regulation is constant.
false
True or false: The rate of transcription initiation rarely influences overall gene expression
false
When the product of a gene produced in a metabolic pathway inhibits an enzyme that acts early on in the pathway it is called
feedback inhibition
In catabolite repression, transcription is influenced by the presence of
glucose
In feedback inhibition, the final product in a metabolic pathway
inhibits an enzyme that acts early in the pathway.
In attenuation, transcription
is stopped prematurely.
It has been shown that the lac operon has three _______ sites to which the lac repressor can bind.
operator
A(n) ______ is a group of two or more genes under the transcriptional control of a single promoter.
operon
An operon encodes a _________ mRNA, an RNA that contains the sequences of two or more genes.
polycistronic
The term _________ regulation refers to control of proteins already present in the cell.
posttranslational
Allolactose is a small effector molecule that binds to the lac repressor and
prevents the repressor from binding to DNA
Anabolic enzymes are usually encoded by ______ operons, and ______ operons usually encode catabolic enzymes
repressible; inducible
An operon is a group of two or more genes under the transcriptional control of _______
single promoter
A translational repressor protein may bind to the mRNA and
stabilize a secondary structure that prevents translation.
Studies indicate that the lac operon has ______ operator site(s) for the lac repressor.
three
the genes in the trp operon :
trp A trp B trp C trp D trp E