KILL ME
According to the crystal structure, to how many lac operator sites does the lac repressor bind at a time?
2
In the trpL gene, which stem-loop together with the U-rich attenuator sequence acts as an intrinsic terminator?
3-4
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 do you call an RNA strand that is complementary to an mRNA molecule?
Antisense RNA
Cyclic-AMP is a small effector molecule produced by the enzyme .
Blank 1: adenylyl, adenyl, or adenylate Blank 2: cyclase
Can a particular segment of mRNA from the trp operon participate in the formation of more than one stem loops at the same time?
No
How does the product of the micF gene regulate the expression of the ompF gene?
The binding of the micF RNA prevents translation of the ompF mRNA.
In which type of regulation do riboswitches control access to the Shine-Dalgarno sequence?
Translation
True or false: The lac repressor does not completely inhibit transcription of the lacZ, lacY, and lacA genes.
True
The binding of ______ to the lac repressor promotes a conformational change that prevents the repressor from binding to the lac operator.
allolactose
In the absence of lactose, the lac repressor
allows very small amounts of the lac enzymes to be made.
Mutations in the gene for the lac repressor that result in a lac repressor that cannot bind allolactose would mean that transcription from the lac operon is
always repressed.
The binding of the lac repressor to the operator shuts down transcription from the lac operon when lactose is Multiple choice question. dep
depleted from the environment.
Many bacterial species use sugars sequentially. This is called
diauxic growth.
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.
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.
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
makes the Shine-Dalgarno sequence available to the ribosome.
Mutations in the gene for the lac repressor that result in a lac repressor that cannot bind DNA would mean that transcription from the lac operon is
not repressible.
A loss-of-function mutation in a gene encoding a repressor protein has the same effect as a mutation in the
operator site.
The conversion of a riboswitch form one conformation to another is due to
the binding of a small molecule.
The small effector molecule prevents the lac repressor from binding to the operator site.
Blank 1: allolactose
A conformational change that prevents the repressor from binding to the lac operator occurs when binds to the lac repressor.
Blank 1: allolactose or lactose
What is the name for a strain of bacteria containing an F' factor?
Merozygote
Select all that apply In the 1950s, ______, ______, and ______ studied mutations in the lac operon of E. coli.
Monod Pardee Jacob
A translational repressor protein may bind to the mRNA and
stabilize a secondary structure that prevents translation.
When lactose is depleted from the environment,
the intracellular concentration of allolactose falls.
anscription begins but terminates before the entire mRNA is made during .
Blank 1: attenuation
The corepressor for a repressible operon may be
the product of that operon.
The mRNA made form the trpL gene contains codons for 14 amino acids that form
the trp leader peptide.
In the trpL mRNA, stem-loops are possible.
Blank 1: three or 3
If a strain of E. coli has a mutation in the lacI gene such that the lac operon is expressed even in the absence of lactose, the expression is called
constitutive.
When four molecules of allolactose are bound to the lac repressor, the lac operon is induced, and RNA polymerase
transcribes the structural genes of the operon.
Riboswitches can regulate
translation. splicing. transcription. RNA stability.
Select the genes in the trp operon.
trpD trpE trpB trpA trpC
The mRNA made from the ______ gene contains codons for 14 amino acids that form the trp leader peptide.
trpL
When attenuation occurs, the mRNA from the trp operon is made as a short piece that terminates shortly past the _____ gene.
trpL
What type of regulation does not need to be adjacent to the gene(s) it is regulating?
Trans-acting factor
In the trp operon, tryptophan acts as
a corepressor.
When tryptophan levels are high, tryptophan binds to Trp repressor protein causing a conformational change that in turn causes the Trp repressor to
bind to the operator site.
In attenuation, transcription
is stopped prematurely.
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.
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.
Blank 1: F' or F'- Blank 2: factor
β-galactosidase activity can be detected using the lactose analog β- because β-glalactosidase cleaves it to a product with a yellow color.
Blank 1: ONPG, o-nitrophenylgalactoside, or beta-nitrophenylgalactoside
The transport of glucose into a bacterial cell causes the intracellular level of cyclic-AMP to fall because the enzyme is inhibited.
Blank 1: adenylyl, adenylate, or adenyl Blank 2: cyclase
The intracellular concentration of the inducer remains high as long as lactose is available in the environment.
Blank 1: allolactose
A regulatory site on a protein where an effector molecule binds is called a(n) site.
Blank 1: allosteric
An enzyme may contain two sites: a catalytic site, and a regulatory or site.
Blank 1: allosteric
The RNA transcribed from the micF gene is complementary to the ompF mRNA and acts as a(n) strand.
Blank 1: antisense
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.
Blank 1: antiterminator
The trp operon is regulated by a repressor protein and by in which transcription is stopped prematurely.
Blank 1: attenuation
Transcription begins but terminates before the entire mRNA is made during .
Blank 1: attenuation
The sequential use of sugars by a bacterial cell is called .
Blank 1: diauxic Blank 2: growth
The small effector molecule produced by the enzyme adenylyl cyclase is ______.
cAMP
When the Lac repressor is bound to the operator, RNA polymerase ______ the lacZ, lacY, or lacA genes.
cannot transcribe
When tryptophan levels in the cell are low, the trp repressor ______ bind to the operator site. RNA polymerase ______ transcribe the trp operon.
cannot; can
In the thi operon in B. subtilis, when levels of TPP are high, the mRNA folds into a stem-loop structure that
causes attenuation.
Monod, Jacob, and Pardee identified rare E. coli mutants that
had abnormal lactose adaptations.
In postranslational regulation, the final product of a metabolic pathway may bind to the site of an enzyme and inhibit its catalytic ability.
Blank 1: allosteric or regulatory
The somewhat imprecise term that describes how transcriptional regulation is influenced by glucose is .
Blank 1: catabolite Blank 2: repression
A DNA segment that must be adjacent to the gene(s) it regulates is a - element.
Blank 1: cis Blank 2: acting
Antisense RNA is an RNA strand that is to an mRNA molecule.
Blank 1: complementary or complimentary
The probability that allolactose will bind to the lac repressor depends on the allolactose in the bacterial cell.
Blank 1: concentration or amount
The product of the biosynthetic activities of the enzymes from an operon may act as a(n) if the operon is repressible.
Blank 1: corepressor or inhibitor
When the product of a gene produced in a metabolic pathway inhibits an enzyme that acts early on in the pathway it is called .
Blank 1: feedback, negative, or feedback inhibition Blank 2: inhibition or feedback
When tryptophan levels in the cell are , translation of the trpL mRNA continues to its stop codon, which terminates further transcription of the operon.
Blank 1: high or sufficient
When four molecules of allolactose are bound to the lac repressor, the repressor can no longer bind to the operator site, and RNA polymerase is free to transcribe the structural genes of the operon, the operon has been .
Blank 1: induced
In the trpL sequence, the 3-4 stem-loop together with the U-rich attenuator sequence acts as a(n) .
Blank 1: intrinsic, rho-independent, or terminator Blank 2: terminator, sequence, or site
For the lac repressor tetramer to bind two operator sites, a must form in the DNA.
Blank 1: loop
or the lac repressor tetramer to bind two operator sites, a must form in the DNA.
Blank 1: loop
It has been shown that the lac operon has three sites to which the lac repressor can bind.
Blank 1: operator
When the lac repressor binds to the lac site, RNA polymerase cannot transcribe the lacZ, lacY or lacA genes.
Blank 1: operator, nucleotides, or O
The term regulation refers to control of proteins already present in the cell.
Blank 1: posttranslational
Types of covalent modification include disulfide bond formation and attachment of prosthetic groups.
Blank 1: posttranslational or post-translational
The TPP riboswitch in E. coli controls , whereas the TPP riboswitch in B. subtilis controls .
Blank 1: translation Blank 2: transcription
What effect would either a loss-of-function mutation in the lacI gene or a mutation in operator that prevents repressor binding have?
Both result in constitutive expression of the lac operon.
Why is transcription of the lac operon low when both lactose and glucose are present?
The low levels of cAMP result in CAP not binding to the CAP site.
Question Mode Multiple Choice Question Mutations in the gene for the lac repressor that result in a lac repressor that cannot bind allolactose would mean that transcription from the lac operon is
always repressed.
During attenuation, transcription begins,
but it is terminated before the entire mRNA is made.
Proteolytic processing, formation of disulfide bonds, and addition of prosthetic groups are all types of
posttranslational covalent modification.
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
When tryptophan levels in the cell are , the trp repressor cannot bind to the site. This allows RNA polymerase to transcribe the genes required for the synthesis of .
Blank 1: low Blank 2: operator Blank 3: tryptophan or trp
A strain of bacteria containing F' factor genes is called a , or a partial diploid.
Blank 1: merozygote
An RNA molecule that can exist in two different secondary conformations and thereby affect gene regulation is known as a(n) .
Blank 1: riboswitch or riboswitches
The mRNA from the trpL genes has four regions that are complementary to each other and cause the mRNA to form -.
Blank 1: stem or hairpin Blank 2: loops
β-ONPG can be used to detect levels of β-galactosidase, because β-galactosidase cleaves β-ONPG into a substance with a ______ color.
yellow
Posttranslational regulation refers to
control of proteins already in the cell.
The mRNA made from the trpL gene has four regions that can
form stem-loops.
In catabolite repression, transcription is influenced by the presence of
glucose.
The transport of ______ into a cell causes a _______ in the concentration of cyclic-AMP by inhibiting adenylate cyclase.
glucose; decrease
When tryptophan levels in the cell are , the ribosome pauses in the trpL mRNA, allowing transcription of the rest of the operon.
Blank 1: low
When both lactose and glucose are absent from bacterial cells, concentrations of cAMP are
high.
In feedback inhibition, the final product in a metabolic pathway
inhibits an enzyme that acts early in the pathway.
When attenuation occurs, the mRNA
is terminated before transcription of the genes required for tryptophan biosynthesis.
When only ______ is present in bacterial cells, cAMP levels are high.
lactose
When both lactose and glucose are present, transcription of the lac operon is
low.
Studies indicate that the lac operon has ______ operator site(s) for the lac repressor.
three
