Chapter 16
Proteins called ______________ transcription factors can initiate transcription only at the basal rate.
general
______________ transcription factors: During formation of the transcription complex, these transcription factors are the first proteins to bind to the promoter.
general
Cell death, cell division, and differentiation are all aspects of this process which establishes body form
morphogenesis
Each specific transcription factor binds to a segment of DNA called a(n) ______________.
operator
Increasing the number of cells without increasing size
cell division
The most efficient control of eukaryotic gene expression is achieved at the level of -replication. -transcription initiation. -post-transcription. -translation initiation. -post-translation.
transcription initiation.
In the presence of tryptophan, tryptophan binds to the -operator. -promoter. -RNA polymerase. -trp genes. -trp repressor.
trp repressor
CAP alone does not bind to DNA, but binding of cAMP to CAP alters its conformation so that it can bind to DNA, t/f
true
In the lac operon, the 3 genes that code for proteins needed to metabolize lactose are transcribed as a unit, producing a single molecule of mRNA, t/f.
true
The lac operon consists of a coding region, which contains 3 genes that code for proteins needed to metabolize lactose, and a regulatory region, which regulates transcription of the coding region, t/f.
true
The presence of glucose blocks induction of the lac operon, t/f
true
When lactose is present, the lac repressor cannot bind to the operator; therefore, RNA polymerase can transcribe the genes that code for proteins needed to metabolize lactose, t/f.
true
The coding region of a gene is located _____________ from its promoter.
upstream
______________ transcription factors: These transcription factors are proteins.
general and specific
______________ transcription factors: These transcription factors form part of the transcription complex
general and specific
The lac operon is expressed when -glucose is high and lactose is present. -glucose is high and lactose is absent. -glucose is low and lactose is present. -glucose is low and lactose is absent. -glucose is low, regardless of the presence or absence of lactose.
glucose is low and lactose is present.
Chromatin that contains highly condensed DNA which is not being expressed is called ________________________
heterochromatin
The structure of chromatin can be modified by altering either the DNA or the ___________ attached to DNA.
histones
In the absence of tryptophan, the trp repressor is -active and can bind to the operator. -active and cannot bind to the operator. -inactive and cannot bind to the promoter. -inactive and can bind to the operator. -inactive and cannot bind to the operator.
inactive and cannot bind to the operator.
A cell-cell interaction that changes the gene expression is called a/an __________________
induction
____________: Response of the lac operon to high levels of lactose
induction
____________: a cell turns on production of a certain enzyme in response to high levels of the substrate
induction
When preparing a presentation on the addition of methyl groups to DNA, the major points to include are -addition of methyl groups does not affect base pairing. -methylation blocks transcriptional activators. -direct inactivation of the genes occurs. -methylation ensures a gene is turned off. -chromatin can be methylated to alter the structure of histones.
-addition of methyl groups does not affect base pairing. -methylation blocks transcriptional activators. -methylation ensures a gene is turned off.
The descriptions that best identify induction of developing cells include: Check all that apply -adjacent cells altering the development of other cells. -signaling molecules between cells altering gene expression. -internal cell molecules accounting for all differentiation in that cell. -growth factors from other cells altering cell differentiation. -pigment granules inside the cell during division determine the cell type.
-adjacent cells altering the development of other cells. -signaling molecules between cells altering gene expression. -growth factors from other cells altering cell differentiation.
The best summary of gene splicing mechanisms are that -they allow one coding sequence to be expressed differently according to each cell type. -it offers gene plasticity to most eukaryotes. -they change all gene types randomly. -it adds yet another layer to gene regulation. -slicing jumps genes to different locations in the genome.
-they allow one coding sequence to be expressed differently according to each cell type. -it adds yet another layer to gene regulation.
The lac repressor is inactivated by binding to which of the following? -Lactose -Betagalactosidase -Transcription factors -Glucose -Allolactose
Allolactose
Enhancers can act at a distance from the gene being transcribed because _______ can form loops.
DNA
In vertebrates, methylation of ____ ensures that once a gene is turned off, it stays off.
DNA
The best description of how regulatory proteins recognize and bind to the correct sequences without unwinding the DNA double helix is -DNA-binding domains can recognize the chemical groups that protrude from the base-pairs into the major groove. -DNA-binding domains can recognize the chemical groups that protrude from the base-pairs into the minor groove. -DNA-binding domains can recognize the chemical groups that protrude from the sugar-phosphate backbone into the major groove. -DNA-binding domains can recognize the chemical groups that protrude from the sugar-phosphate backbone into the minor groove. -Regulatory proteins have DNA-binding domains that are inserted into the major groove and can recognize the shape of each nitrogenous base.
DNA-binding domains can recognize the chemical groups that protrude from the base-pairs into the major groove.
Why does the concentration of glucose have an effect on the transcription of the lac operon? -The lac operon functions to metabolize glucose, lactose, and other small sugars. -Glucose is an important cell signaling molecule. -Glucose is the preferred sugar for the bacteria. If it is present, lactose metabolism is suppressed. -Glucose is a precursor of lactose. -All of these are true.
Glucose is the preferred sugar for the bacteria. If it is present, lactose metabolism is suppressed.
Bacteria in your lab are grown under two conditions, one with exposure to glucose and the other with lactose. What best describes the effects glucose will have upon the enzymes used to metabolize lactose? -The enzymes needed to metabolize lactose are inhibited. -Induction of the enzymes is reduced. -Glucose will turn off all trp genes. -Glucose repression stops the lac operon from being induced. -Nothing as the enzymes that metabolize both lactose and glucose are the same.
Glucose repression stops the lac operon from being induced.
Evaluate the statements below and determine which is the BEST reason that bacterial cells use operons and polycistronic RNA. -Initiation of all genes in a biochemical pathway are regulated simultaneously. -Operons are more stable than structural genes that are located singly on a chromosome. -Bacterial cells have small genomes that cannot accommodate large numbers of regulatory regions. -Bacterial cells have a short life span, and transcribing genes singly will take too long. -Bacterial genes are very short, so RNA that is not polycistronic might be mistaken for fragments that should be digested.
Initiation of all genes in a biochemical pathway are regulated simultaneously.
At which of the following level(s) can gene expression be regulated in eukaryotes? -Passage of mRNA through the nuclear membrane. -Destruction of the mRNA. -Rate of protein synthesis. -Passage of mRNA through the nuclear membrane and destruction of the mRNA. -Passage of mRNA through the nuclear membrane, destruction of the mRNA, and rate of protein synthesis.
Passage of mRNA through the nuclear membrane, destruction of the mRNA, and rate of protein synthesis.
Transcription is carried out by the enzyme -DNA polymerase. -RNA polymerase. -RNAse. -topoisomerase. -reverse transcriptase.
RNA polymerase
General transcription factors, along with TAFs, recruit _________________ and position it at the start of the protein-coding sequence.
RNA polymerase II
Evaluate the statements and determine which is the best explanation for why eukaryotes use so many regulatory elements, such as activators, repressors, coactivators, and basal transcription factors -The complexity is a result of multiple gene duplication events. -The complexity ensures that a single mutation cannot effect the function of the protein. -The complexity allows specific control over the timing and quantity of the protein produced. -The complexity allows more than one protein to be transcribed by a single RNA Polymerase. -The complexity is necessary because RNA polymerase cannot efficiently bind to the DNA by itself.
The complexity allows specific control over the timing and quantity of the protein produced.
A mutation causes an activator to be nonfunctional. Which of the following statements best describes the consequences? -The gene will not be expressed. -The gene will be expressed, but in less than optimal quantities. -The gene will be over expressed. -The gene will be expressed constitutively. -The gene will be expressed as normal.
The gene will be expressed, but in less than optimal quantities.
If the operator (lacO) was mutated, what effect would this have on lactose metabolism? -The repressor would not properly bind to the operator, and the lac operon would be over expressed. -The repressor would not properly bind to the operator, and the lac operon would be under expressed. -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. -RNA polymerase would not properly bind to the promoter, and the lac operon would be under expressed. -The repressor protein would not be produced, and the lac operon would be over expressed.
The repressor would not properly bind to the operator, and the lac operon would be over expressed.
What statement about basal transcription factors is true? -Their binding prevents the binding of RNA polymerase to the promoter. -They can increase the rate of transcription by themselves. -They can decrease the rate of transcription by themselves. -They are essential for transcription. -They bind to sites that are distant from the promoter.
They are essential for transcription.
What statement about enhancers is true? -They are sequences to which activators bind. -They are basal transcription factors. They are essential for transcription. -They are proteins that link basal transcription factors to activators. -They are found within the promoter of a gene.
They are sequences to which activators bind.
How does glucose effect the lac operon? -When glucose levels are high, glucose binds to and deactivates the repressor, preventing it from binding to the DNA. -When glucose levels are low, glucose binds to and activates the repressor, causing it to associate with the DNA. -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. -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. -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.
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.
Is it theoretically possible to generate an entire animal from a somatic (body) nucleus? -Yes, because like plants, animals normally generate the entire organism from differentiated parts. -No, because a somatic nucleus contains only some of the genes of the organism. -No, because most animals do not show regeneration after large injuries. -Yes, because a somatic nucleus contains all the genetic information present in the zygote. -No, because epigenetic changes have caused changes in the DNA sequences.
Yes, because a somatic nucleus contains all the genetic information present in the zygote.
______________ transcription factors: These transcription factors include TFIID and TFIIE
general
The________________ of histones tends to loosen the coiling of DNA, making it more accessible for transcription.
acetylation
In the absence of lactose, the lac repressor is -active and can bind to the operator. -active and cannot bind to the operator. -inactive and cannot bind to the promoter. -inactive and can bind to the operator. -inactive and cannot bind to the operator.
active and can bind to the operator.
When in a complex with ________, the CAP protein binds to the CAP site and ________ the expression of the lac operon. -glucose ; switches on. -glucose ; switches off. -lactose ; switches on. -cAMP ; switches on. -cAMP ; switches off.
cAMP ; switches on.
A cell in an embryo will produce intestinal cells later in development. When that cell is removed and grown separated from the embryo, it produces muscles instead. This means that in order to make intestinal cells, a/an _________________________ is necessary.
cell-cell interaction
In some cells, DNA combines with proteins to form a substance called _____________.
chromatin
Some activators interact directly with RNA polymerase II while others require the assistance of a(n) _______________-
coactivator
If cells from one part of an embryo are transplanted to another part, and they develop into the tissue they would have made originally, the cells are said to be _______________>
determined
Cell specialization through selective gene expression.
differentiation
A(n) _______________ is a regulatory protein that acts to increase the rate of transcription above the basal rate.
enhancer
Chromatin that contains loosely coiled DNA, which is accessible for transcription, is called _______________
euchromatin
Chromatin is present in _______________ cells only.
eukaryotic
Synthesis of the proteins needed to metabolize lactose is repressed by the presence of lactose, t/f.
false
The coding region of the lac operon is transcribed when the CAP-cAMP complex is bound to the CAP binding site and the lac repressor is bound to the operator, t/f
false
The lac operon is positively regulated by the lac repressor, t/f.
false
When lactose is absent, the lac repressor binds to the promoter and blocks transcription of the genes that code for proteins needed to metabolize lactose, t/f
false
When the CAP-cAMP complex binds to the CAP binding site, this bends the DNA which blocks binding of RNA polymerase to the promoter, t/f.
false
When the level of glucose is high, cAMP is abundant and binds to CAP, t/f.
false
The reason why different cells turn into different tissues is because of differences in __________________.
gene expression
______________ transcription factors: One of these transcription factors binds directly to the TATA box in the core promoter
general
______________ transcription factors: These transcription factors are necessary to recruit RNA pol II to the promoter and initiate transcription at the basal level
general
You and a group of scientists are mapping out gene regulation in a new species. Based on what is currently known about control of gene expression, the control point to begin your study at would be -degradation of mRNA. -splicing of mRNA. -the passage of mRNA through the nuclear membrane. -initiation of transcription. -initiation of translation. -posttranslational modification of proteins.
initiation of transcription.
With cytoplasmic determinants, a cell will become committed to a particular future because it has inherited a particular mRNA or protein from ___________________
its mother
How does the cell recognize that lactose needs to be metabolized? -lactose directly activates the transcription of the lac operon. -lactose stimulates a transcription factor that activates transcription of the lac operon. -lactose is converted into allolactose, which inhibits the lac repressor. -lactose is converted into beta-galactosidase, which inhibits the lac repressor. -lactose stimulates the production of cAMP, which activates kinases that activate transcription of the lac operon.
lactose is converted into allolactose, which inhibits the lac repressor.
Tighter coiling of the chromatin makes the DNA _______ accessible for transcription.
less
The ______________ of histones is correlated with tighter coiling of the DNA and inactive regions of chromatin.
methylation
In general, cells from early stage embryos are able to make __________ cell types compared with cells from later stage embryos
more
Large chromatin-remodeling complexes alter the structure of chromatin in order to make the DNA ________ accessible to regulatory proteins which, in turn, affect gene expression
more
The lowest level of chromatin structure consists of DNA wrapped twice around a group of histones to form a(n) ______________.
nucleosome
A new pesticide targeting insects has been designed to interfere with cytoplasmic determinants. The most accurate outcome from exposure to this pesticide would be -unregulated cell growth and differentiation causing death in all insects. -adult insects becoming sterile and unable to reproduce. -all insects suffocating due to reduced oxygen transfer during cell division. -embryonic mutations due to interrupted development during differentiation. -offspring that would not be physically formed properly during determination.
offspring that would not be physically formed properly during determination.
Orientation of cells by the detection of positional information
pattern formation
Formation of the transcription initiation complex begins when general transcription factors bind to a segment of DNA called the ___________.
promoter
RNA polymerase binds to the -operator. -promoter. -regulator. -terminator. -enhancer.
promoter
The formation of nucleosomes may block the binding of transcription factors and RNA polymerase II to the________________
promoter
____________: A cell turns off production of certain enzyme in response to high levels of the product
repression
____________: Response of the trp operon to high levels of tryptophan
repression
______________ transcription factors: These transcription factors act in a tissue- or time dependent manner to stimulate levels of transcription that are higher than the basal level
specific
