ch 14 gene regulation
post-translational gene regulation
-a phosphate group is added to a protein, making it inactive -the rate of a degradation of a protein is increased
transcriptional gene regulation
-an activator binds to an enhancer -a repressor binds to a near promotor
translational gene regulation
-the ability of an mRNA to bind to its ribosomes is changed -the 5' end of an mRNA forms a shape that blocks translation
post-transcriptional gene regulation
-the correct removal of introns of a pre-mRNA is prevented -stability of an mRNA is regulated -export of an mRNA to the cytoplasm is blocked
why are molecules other than RNA polymerase needed for transcription?
RNA polymerase is the molecule that makes mRNA. however it is not the only molecule needed for transcription. other molecules recognize the site where transcription should start and create a complex that allows RNA polymerase to bind to the DNA and begin RNA synthesis. RNA polymerase does not have the ability to detect where it should start making mRNA. without an initiation complex mRNA synthesis might start at random locations. other molecules control the rate of mRNA synthesis. not all gene products are required in equal amounts so other molecules are used to increase or decrease the rate of synthesis
in the absence of lactose, the lac repressor is _______________ a) active and can bind to the operator b) active and cannot bind to the operator c) inactive and cannot bind to the promoter d) inactive and can bind to the operator e) inactive and cannot bind to the operator
a) active and can bind to the opereator
which of the following statements about enhancers is TRUE? a) enhancers are sequences to which activators bind b) enhancers are found in the promoter of a gene c) enhancers are only found in certain chromosomal locations d) enhancers are sequences to which activators bind and they are found in the promoter of a gene e) enhancers are found in the promoter of a gene, and they are only found in certain chromosomal locations
a) enhancers are sequences to which activators bind
what is the MOST important reason a cell exhibits tight transcriptional control over the regulation of gene expression? a) regulation at the transcriptional level is energetically efficient for the cell b) cells can only regulate the concentration of protein at the transcriptional level c) at the transcriptional level, mRNA can be degraded quickly to lower their concentration in the cytoplasm d) at the transcriptional level, protein synthesis can be turned on and off quickly to respond to the needs of the cell e) regulation at the transcriptional level can affect the differentiation of future generations of cells
a) regulation at the transcriptional level is energetically efficient for the cell *if a protein is not needed, it is most energetically efficient not to synthesize RNA- an energetically expensive process
if lacO were mutated, what effect would this have on lactose metabolism? a) the repressor would not properly bind to the operator, and the lac operon would never be expressed b) the repressor would not properly bind to the operator, and the lac operon would be under expressed c) RNA polymerase would not properly bind to the promoter, and the lac operon would be under expressed d) the repressor protein would not function properly, and the lac operon would be over expressed
a) the repressor would not properly bind to the operator, and the lac operon would be over expressed
the cell is capable of regulating gene expression in a variety of situations and environments. valid reasons for a cell to regulate gene expression include its ability to: a) make additional cells of the same type in response to a demand b) synthesize enzymes to metabolize a particular nutrient c) keep a gene product available under all conditions d) execute a specific program of development (e.g. to become a blood cell or immune cell) e) stop synthesis of a cellular component when there is enough available in the cell f) synthesize mRNA for every gene in the genome at all times
a) true b) true c) false bc a cell would regulate gene expression to make a gene product available only when the cellular conditions warrant it, not under all conditions d) true e) true f) false bc a cell would regulate gene expression to synthesize mRNA of genes only when the gene product is needed, not at all times
the assembly of transcription factors begins _____________ a) upstream from the transcription start site b) downstream from the transcription start site c) upstream from the translation start site d) downstream from the translation start site e) downstream from the translation stop site
a) upstream from the transcription start site
transcription is carried out by the enzyme a) DNA polymerase b) RNA polymerase c) RNase d) topoisomerase e) reverse transcription
b) RNA polymerase
small RNAs, typically 22 nucleotides long, that function in post-transcriptional regulation of gene activity are produced a) by transcription of genes called small DNAs b) by digestion of double-stranded RNA into smaller pieces c) when a mRNA is recycled by the cell d) by ligation of individual ribonucleotide monophosphates (rNMPs) e) when small DNAs are converted into RNA by enzymes
b) by digestion of double-stranded RNA into smaller pieces
the lac repressor binds to what site within the lac operon? a) lacZ b) lacO c) lacA d) lacI e) lacP
b) lacO
RNA polymerase binds to the _______________ a) operator b) promoter c) regulator d) terminator e) enhancer
b) promoter
which of the following best describes the consequence of a mutated activator on expression of a transcriptional target gene? a) the gene will not be expressed b) the gene will be expressed, but in less than optimal quantities c) the gene will be over expressed d) the gene will be expressed constituently e) the gene will be expressed normal
b) the gene will be expressed, but in less than optimal quantities
the most effiecient control of eukaryotic gene expression is achieved at the level of ______________ a) replication b) transcription initiation c) post-transcription d) translation initiation e) post-translation
b) transcription initiation
a regulatory element that can function from a large distance (e.g. tens of thousands of base pairs) from a promoter is called ___________________ a) an inducer b) a repressor c) an enhancer d) a core promoter e) a histone
c) an enhancer
the lac operon is expressed when ____________ a) glucose is high and lactose is present b) glucose is high and lactose is absent c) glucose is low and lactose is present d) glucose is low and lactose is absent e) glucose is low, regardless of the presence or absence of lactose
c) glucose is low and lactose is present
why does the concentration of glucose have an effect on the transcription of the lac operon? a) the lac operon functions to metabolize glucose, lactose, and other small sugars b) glucose is an important cell signaling molecule c) glucose is the preferred sugar for the bacteria. if it is present, lactose metabolism is supressed d) glucose is a precursor of lactose e) all of the answers are correct
c) glucose is the preferred sugar for the bacteria. if it is present, lactose metabolism is supressed
which region associated with the lac operon is not involved in binding of RNA polymerase? a) CAP binding sit b) lacO c) lacZ
c) lacZ
how does the cell recognize that lactose needs to be metabolized? a) lactose directly activates the transcription of the lac operon b) lactose stimulates a transcription factor that activates transcription of the lac operon c) lactose is converted into allolactose, which inhibits the lac repressor d) lactose is converted into beta-galactosidase, which inhibits the lac repressor e) lactose stimulates the production of cAMP, which activates kinases that activate transcription of the lac operon
c) lactose is converted into allolactose, which inhibits the lac repressor
what protein would not interact with a coactivator? a) activators b) multiple activators simultaneously c) repressors d) basal transcription factors e) all of these would interact with the coactivators
c) repressors
which of the following statements is the best explanation for why eukaryotes use so many regulatory elements, such as activators, repressors, coactivators, and basal transcription factors? a) the complexity is a result of multiple gene duplication events b) the complexity ensures that a single mutation cannot effect the function of the protein c) the complexity allows specific control over the timing and quantity of the protein produced d) the complexity allows more than one protein to be transcribed by a single RNA polymerase e) the complexity is necessary because RNA polymerase cannot efficiently bind to the DNA by itself
c) the complexity allows specific control over the timing and quantity of the protein produced
which of the following statement(s) about basal transcription is(are) TRUE? a) they are essential to transcription b) they cannot increase the rate of transcription by themselves c) they can decrease the rate of transcription by themselves d) they are essential for transcription and they cannot increase the rate of transcription by themselves e) they are essential for transcription, they cannot increase the rate of transcription by themselves, and they can decrease the rate of transcription by themselves
c) they are essential for transcription and they cannot increase the rate of transcription by themselves
which statement represents the best explanation for why eukaryotes use basal, or general, transcription factors? a) RNA polymerase cannot bind to the DNA without their aid b) they interact with coactivators c) they give the cell tight control over transcription d) eukaryotes do not use sigma factor e) they allow RNA polymerase to locate the promoter
c) they give the cell tight control over transcription
DNA is associated with proteins to form _____________
chromatin
what is the MOST important reason a cell would have translational control over the regulation of gene expression? a) regulation at the translation level is the most energetically efficient for the cell b) cells can best regulate the concentration of protein at the translation level c) at the translational level, mRNA can be degraded quickly to lower the protein concentration in the cytoplasm d) at the translational level, protein synthesis can be turned on and off quickly to respond to the needs of the cell e) regulation at the translational level can affect the differentiation of future generations of cells
d) at the translational level, protein synthesis can be turned on and off quickly to respond to the needs of the cell *a response can be affected quickly if the mRNA is already synthesized
when in a complex with _________, the CAP protein binds to the CAP site and ____________ the expression of the operon a) glucose; switches on b) glucose; switches off c) lactose; switches on d) cAMP; switches on e) cAMP; switches off
d) cAMP; switches on
select the BEST description of the complexity of eukaryotic gene expression as compared to prokaryotic gene expression a) eukaryotes have much larger genomes than prokaryotes b) eukaryotes have linear chromosomes while prokayotes have circular chromosomes c) eukaryotic mRNA molecules usually code for a single structural gene while prokaryotic mRNA are generally polycistronic d) eukaryotic transcription is usually influenced by many transcription factors while prokarytoic transcription is usually influenced by only a few transcription factors e) eukaryotic transcription involves general transcription factors while prokaryotic transcription involves an operator
d) eukaryotic transcription is usually influenced by many transcription factors while prokaryotic transcription is usually influenced by only a few transcription factors
which of the following is not part of the lac operon? a) lacO b) lacZ c) lacA d) lacI e) lacP
d) lacI
which of the following statements about basal transcription is TRUE? a) they are essential for transcription b) they cannot increase the rate of transcription by themselves c) they can decrease the rate of transcription by themselves d) they are essential for transcription and they cannot increase the rate of transcription by themselves e) they are essential for transcription, they cannot increase the rate of transcription by themselves, and they can decrease the rate of transcription by themselves
d) they are essential for transcription and they cannot increase the rate of transcription themselves
What level of regulation do eukaryotes possess that prokaryotes do not? a) initiation of transcription b) initiation of translation c) rate of elongation during translation d) transport of RNA out of the nucleus e) degradation of mRNA
d) transport of RNA out of the nucleus
how does glucose affect the lac operon? a) when glucose levels are high, glucose binds to and deactivates the repressor, preventing it from binding to the DNA b) when glucose levels are low, glucose binds to and activates the repressor, causing it to associate with DNA c) when glucose levels are low, it stimulates the production of cAMP, which binds to and deactivates the repressor, preventing it from binding to the DNA d) when glucose levels are low, it stimulates the production of cAMP, which binds to and activates the CAP protein, allowing it to bind the DNA e) when glucose levels are high, it stimulates the production of cAMP, which binds to and deactivates the CAP protein, preventing it from binding to the DNA
d) when glucose levels are low, it stimulates the production of cAMP, which binds to and activates the CAP protein, allowing it to bind to the DNA
removal of acetyl groups from histones results in a/an _____ in gene expression.
decrease
assembly of basal transcription factor begins at the __________ sequence in the promoter a) GGCC b) AATT c) ACGT d) GAGA e) TATA
e) TATA
how would an activator influence gene expression at a promoter far away from the place that it binds DNA? a) the activator methylates the DNA and this causes long-distance activation b) the activator directly binds to RNA polymerase, which then skips over a large region of DNA to start transcription c) ribosomes are recruited to the promoter by the activator d) histone proteins are modified to create a closed conformation e) a mediator protein is stimulated by the bound activator, and then the mediator stimulates transcription
e) a mediator protein is stimulated by the bound activator, and then the mediator stimulates transcription
the lac repressor is inactivated by binding to which of the following? A) lactose B) betagalactosidase C) transcription factors D) glucose E) allolactose
e) allolactose
how is it possible for a single gene to encode more than one polypeptide? a) a single transcription factor can regulate many genes b) the exons in DNA can undergo a shuffling process during S phase c) it is not possible; this violates the "one gene--one enzyme" hypothesis d) mRNA bases can be rearranged in a molecular fashion e) introns can be removed from pre-mRNA in different combinations
e) introns can be removed from pre-mRNA in different combinations
at which of the following level(s) can gene expression be regulated in eukaryotes? a) passage of mRNA through the nuclear membrane b) destruction of the mRNA c) rate of protein synthesis d) passage of mRNA through the nuclear membrane and destruction of the mRNA e) passage of mRNA through the nuclear membrane, destruction of the mRNA, and rate of protein synthesis
e) passage of mRNA through the nuclear membrane, destruction of the mRNA, and rate of protein synthesis
If lacI were mutated such that could no longer bind DNA, what effect would this have on the regulation of the operon? a) one of the enzymes that are involved in lactose metabolism would not be able to carry out its reaction, and lactose would not be metabolized b) the cell would not be able to recognize the presence of lactose, and the lac operon would be under expressed c) RNA polymerase would not properly bind to the promoter, and the lac operon would be under expressed d) the repressor protein would not function properly, and the lac operon would be over expressed
e) the repressor protein would not function properly, and the lac operon would be over expressed
an activator can increase transcription by attraction a ____________________ to the region
histone acetyltransferase
what is meant by gene activation?
in a multicellular organism every cell contains every gene found in the organism. not all genes are usually used in every cell. the specialization of cell into different types means that some genes are used in some cells and not in other. also many genes are only used at certain times.
addition of (-COCH₃) groups to histone amino terminal tails results in a/an _____ in gene expression.
increase
a ________________ is composed of DNA wrapped around an octamer of histone proteins
nucleosome
why are several genes for different products involved in the same pathway located next to one another in the genome?
the lac operon contains DNA sequences coding for three enzymes involved in the fermentation of lactose. when, transcription is initiated the mRNA for all three enzymes is transcribed as a unit. if one protein is made then all three are made. this is only possible because the DNA sequences for all three genes are located next to one another. when, RNA polymerase activity is initiated it can transcribe the mRNA that includes all three genes. if the three genes were in different locations the transcription of each one would have to be controlled separately
how are genes turned on and off?
there are many different mechanisms for controlling transcription of mRNA. if a gene is 'turned on' then transcription proceeds followed by translation and production of a protein. if a gene is 'turned off' then the transcription is halted. different kinds of cells have different patterns of transcription ( known as gene expression). gene expression also varies within a cell depends on the influence of external factors.
