Chapter 14-
Studies indicate that the lac operon has ______ operator site(s) for the lac repressor.
3
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.
Why does transcription of the trp operon continue when tryptophan levels are low?
The ribosome pauses in region 1, preventing the 3-4 stem-loop from forming.
An operon is a group of two or more genes under the transcriptional control of ______.
a single promoter
In the thi operon, when levels of TPP are low, the 5' end of the mRNA forms an ______ stem-loop structure that allows transcription to continue.
antiterminator
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
During attenuation, transcription begins, ____
but it is terminated before the entire mRNA is made
During attenuation, transcription begins, ______.
but it is terminated before the entire mRNA is made
When the lac repressor is bound to the operator, RNA polymerase ______ the lacZ, lacY, or lacA genes.
cannot transcribe
Inducible operons usually encode ______ enzymes, and repressible operons usually encode ______ enzymes.
catabolic; anabolic
Select the genes in the trp operon.
trpE trpC trpA trpD trpB
The somewhat imprecise term that describes how transcriptional regulation is influenced by glucose is _____
catabolite repression
Posttranslational regulation refers to ______.
control of proteins already in the cell
The research of Monod and Jacob that led to the initial understanding of gene regulation stemmed from an interest in ______.
enzyme adapation
The genes in the trp operon encode _____
enzymes used in tryptophan biosynthesis
True or false: Gene expression is always the same
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
In attenuation, transcription ______
it stopped prematurely
When the tryptophan level in the cell is ______, the ribosome pauses in region one of the trpL mRNA, causing region 2 to to bind to region 3 and transcription to continue.
low
A translational repressor recognizes sequences within ______ and ______ translation.
mRNA; inhibits
A polycistronic mRNA contains the sequence(s) ______.
of 2+ genes
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
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
In the thi operon, when levels of TPP are low, the mRNA folds into a stem-loop structure that ______.
prevents formation of the terminator stem-loop
The phenomenon in which the level of gene expression can vary under different conditions is gene_____
regulation
Anabolic enzymes are usually encoded by ______ operons, and ______ operons usually encode catabolic enzymes.
repressible; inducible
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
An RNA molecule that can exist in two different secondary conformations and thereby affect gene regulation is known as a(n) ____
riboswitch
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
Riboswitches can regulate ______.
transcription or translation
The TPP riboswitch in E. coli controls _____ , whereas the TPP riboswitch in B. subtilis controls _____ .
translation; transcription
The TPP riboswitch in E. coli controls ______ , whereas the TPP riboswitch in B. subtilis controls ______.
translation; transcription
A regulatory protein that inhibits translation is called a ______
translational repressor
