Chapter 16 ( homework Q)
Transcription of the lac operon results in the production of how many different mRNA transcripts?
1
which of the following combinations would cause transcription to increase?
a repressor plus an inducer
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 intracellular concentration of the inducer _____ remains high as long as lactose is available in the environment.
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
Regulation of the trp operon involves the process of_____ , in which transcription begins but terminates before the entire mRNA is made
attenuation
The trp operon is regulated by a repressor protein and by ______, in which transcription is stopped prematurely.
attenuation
Tryptophan associates with the _____. This complex can then _____ to the trp operator and inhibit transcription.
bind; trp operator
The lac repressor protein binds to the operator and ______.
blocks transcription
During attenuation, transcription begins ______.
but is terminated before the entire mRNA is made
Inducible operons usually encode ______ enzymes, and repressible operons usually encode ______ enzymes.
catabolic; anabolic
The somewhat imprecise term that describes how transcriptional regulation is influenced by glucose is____ ______
catabolite repression
In the thi operon in B. subtilis, when levels of TPP are high, the mRNA folds into a stem-loop structure that ______.
causes attenuation
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
The probability that allolactose will bind to the lac repressor depends on the allolactose _______ in the bacterial cell.
concentration
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 ______ the environment.
depleted from
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 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
True or false: The rate of transcription initiation rarely influences overall gene expression.
false
Consider a case where the end product of a metabolic pathway inhibits an enzyme that acts early on in the pathway. This mechanism of regulation is called ______
feedback inhibition
During attenuation, when tryptophan levels are _____, the ___stem-loop forms and transcription stops.
high;3-4
In feedback inhibition, the final product in a metabolic pathway ______.
inhibits an enzyme that acts early in the pathway
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 ______.
makes the Shine-Dalgarno sequence available to the ribosome
A strain of bacteria containing F' factor genes is called a(n) _____, or a partial diploid.
merozygote
A(n)_______ is a group of two or more genes under the transcriptional control of a single promoter.
operon
An operon encodes a(n) _______ mRNA, an RNA that contains the sequences of two or more genes.
polycistronic
An operon encodes a(n) ________mRNA, an RNA that contains the sequences of two or more genes.
polycistronic
Control of proteins already present in the cell is called_____ regulation
posttranslational
Allolactose is a small effector molecule that binds to the lac repressor and ______.
prevents the repressor from binding to DNA
The tryptophan operon produces proteins that are involved in the biosynthesis of tryptophan. Like some other biosynthetic operons it is regulated by the final _____ of the biosynthetic pathway, which ____ transcription of the operon.
product; represses
In bacteria, the most common way to regulate gene expression is by influencing the ______.
rate of transcription initation
A repressor is a ______ that _____ transcription
regulatory protein; inhibits
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
When lactose is depleted from the environment, the _______.
the intracellular concentration of allolactose falls
Studies indicate that the lac operon has ______ operator site(s) for the lac repressor
three
What type of regulator does not need to be adjacent to the gene(s) it is regulating?
trans-acting factor
Which of the following can be regulated by riboswitches?
transcription translation splicing RNA stability
If a riboswitch controls access to the Shine-Dalgarno sequence, which of the following will be regulated?
translation
list the genes in the trp operon.
trpA-trpE
A polycistronic mRNA contains the sequence(s) for _____
two or more genes