draft chapter 14 gene regulation in bacteria
what kind of genes encode proteins that are needed for bacterium survival
constitutive genes
which data provide the strongest evidence that O1 is not the only operator site?
data where O2 and O3 are deleted indicate O1 by itself is not the only operator site
refers to control of proteins already present in the cell:
posttranslational regulation
a repressor is a _______ that ________ transcription
regulatory protein, inhibits
An RNA molecule that can exist in two different secondary conformations and thereby affect gene regulation is known as a(n)
riboswitch
a _____ is a protein that influences the ability of RNA polymerase to transcribe a given gene.
transcription factor
Studies indicate that the lac operon has ______ operator site(s) for the lac repressor.
3
What effect can ATP-dependent chromatin remodeling have on transcription? Neither activation nor repression Both activation and repression Activation only Repression only
Both activation and repression
which of the following combinations will cause the rate of transcription to increase? a. a repressor plus an inducer b. a repressor plus a corepressor c. an activator plus an inhibitor d. none of the above will increase the rate of transcription
a. a repressor plus an inducer
The binding of __________ to the lac repressor causes the lac repressor to _________ to the operator site, thereby ________ transcription
allolactose, not bind, increasing
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
Transcription begins but terminates before the entire mRNA is made during ______
attenuation
regulatory proteins
bind to DNA and affect rate .....
The function of TFIID is to ______. bind to the core promoter and recruit RNA polymerase II to the TATA box bind to an enhancer to increase transcription from the core promoter bind to the TATA box and recruit RNA polymerase II to the core promoter prevent the binding of RNA polymerase II to the core promoter
bind to the TATA box and recruit RNA polymerase II to the core promoter
During attenuation, transcription begins, ______. but then a repressor protein binds to the operator and continues beyond the operon but it is terminated before the entire mRNA is made but translation stops after the eighth codon
but it is terminated before the entire mRNA is made
The CREB protein is a regulatory transcription factor that is activated following an increase in ______. cAMP glucocorticoid hormones RNA steroid hormones
cAMP
how does exposing an E coli cell to glucose affect the regulation of the lac operon via CAP?
cAMP does not bind to CAP and transcription is decreased
In feedback inhibition, the final product in a metabolic pathway ______. causes the formation of a stem-loop structure in the mRNA that prevents translation prevents translation of its own mRNA inhibits an enzyme that acts early in the pathway causes increased production of enzymes that act early in the pathway
causes increased production of enzymes that act early in the pathway
response to environmental stress
certain proteins help a bacterium survive an environmental stress, like osmotic shock or heat shock (only required when confronted with stress)
unregulated genes are also called _____
constitutive genes
Posttranslational regulation refers to ______. control of transcription initiation regulation of translation of mRNAs regulation of transcription termination control of proteins already in the cell
control of proteins already in the cell
Transcription factor proteins contain regions called ____ that specific functions
domains
what is a benefit of gene regulation?
efficient in terms of ENERGY USE (encoded proteins are produced only when they are required, cell avoids wasting valuable energy making proteins it doesn't need)
The binding of a regulatory transcription factor to a(n) ______________ can stimulate transcription 10- to 1000-fold, which is called ________ regulation.
enhancer, up
True or false: The rate of transcription initiation rarely influences overall gene expression. True false
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 initiation
Gene regulation means that ______. gene expression is controlled so that all genes in a genome are expressed at the same level gene expression can be controlled so that genes can be expressed at high or low levels only certain genes are included in the genome of a species
gene expression can be controlled so that genes can be expressed at high or low levels
The phenomenon in which the level of gene expression can vary under different conditions is:
gene regulation
In catabolite repression, transcription is influenced by the presence of _____. glucose lactose fructose galactose
glucose
what is an operon?
group of genes under the control of a single promoter
the most common way to regulate gene expression:
influence the rate at which transcription is initiated
which genes are under the control of the lac promoter?
lacZ, lacY, lacA genes
what is a more accurate way than saying genes being turned on/off
level of gene expression is increased/decreased
A translational repressor recognizes sequences within ______ and ______ translation. DNA; inhibits mRNA; increases mRNA; inhibits tRNA; increases rRNA; inhibits
mRNA, inhibits
If chromatin is in a closed conformation, nucleosome position and histone composition ______. make it easier for the DNA to become single stranded during transcription make it difficult for the DNA to become single stranded during transcription enhance the ability of transcription factors to gain access to and bind their target sequences in the promoter DNA make it difficult for transcription factors to gain access to and bind their target sequences in the promoter DNA
make it difficult for transcription factors to gain access to and bind their target sequences in the promoter DNA
3 common processes regulated at the genetic level
metabolism, response to environmental stress, cell division
____ can change in location along a DNA molecule, by replacement of a standard histone with a histone variant, and through covalent modifications on histone tails.
nucleosomes
gene regulation
phenomenon in which the level of gene expression can vary under different conditions
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 causes attenuation causes premature termination of transcription prevents the ribosome form binding to the start codon
prevents formation of the terminator stem-loop
cell division
some proteins are needed for cell division (necessary only when the cell is about to divide)
metabolism
some proteins function in the metabolism of small molecules, certain enzymes are needed for a bacterium to metabolize particular sugars (enzymes are only required when sugar is present in the environment)
Regulatory transcription factors that respond to steroid hormones are called:
steroid receptor
In bacteria, the most common way to regulate gene expression is by influencing ______. the frequency of cell division the rate of transcription elongation the rate of translation initiation the rate of transcription initiation
the rate of transcription initiation
why is it beneficial for the bacterium to regulate the lac operon with both a repressor protein and an activator protein?
the repressor protein allows the cell to avoid turning on the operon in absence of lactose. The activator protein allows the cell to choose between glucose and lactose
Riboswitches can regulate ______. transcription only posttranslational modification transcription or translation translation only
transcription or translation
A regulatory protein that inhibits translation is called a
translational repressor
Most histone genes encode standard histone proteins, but some have accumulated mutations that change the amino acid sequence of the histone proteins. These proteins are called histone ___
variants
The function of regulatory transcription factors must be modulated to ensure that genes are turned on ______. in growing cells only all the time under the appropriate environmental conditions in the correct cell type at the proper time
under the appropriate environmental conditions in the correct cell type at the proper time
what kind of genes have constant levels of expression?
unregulated genes (constitutive genes)
An enhancer is a DNA element that can be bound to a regulatory transcription factor, which leads to ______. transcriptional repression down regulation up regulation DNA replication
up regulation
What affect does acetylation have on lysines in core histone protein tails? Eliminates the negative charge on lysine, disrupting the electrostatic attraction between the histone and the positively charged DNA backbone Reason: The lysine side chain has a positive charge. Makes an additional negative charge on lysine, causing the DNA and the histone to repel one another Makes an additional positive charge on lysine, causing the DNA to bind more strongly to the histone Eliminates the positive charge on lysine, disrupting the electrostatic attraction between the histone and the negatively charged DNA backbone
Eliminates the positive charge on lysine, disrupting the electrostatic attraction between the histone and the negatively charged DNA backbone
The conversion of a riboswitch form one conformation to another is due to ______. a corepressor the covalent modification of the final product the binding of a small molecule the presence of CAP
the binding of a small molecule
under what condition is lac repressor bound to the lac operon?
the repressor protein is bound to the lac operon when allolactose is not bound to the repressor, which occurs when lactose is not available