BIOL 3025
If lacI were mutated such that could no longer bind DNA, what effect would this have on the regulation of the operon? A) The repressor protein would not function properly, and the lac operon would be over expressed. B) RNA polymerase would not properly bind to the promoter, and the lac operon would be under expressed. C) 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. D) The cell would not be able to recognize the presence of lactose, and the lac operon would be under expressed.
A
Small RNAs, typically 22 nucleotides long, that function in post-transcriptional regulation of gene activity are produced A) by digestion of double-stranded RNA into smaller pieces. B) by transcription of genes called small DNAs. C) by ligation of individual ribonucleoside monophosphates (rNMPs). D) when a mRNA is recycled by the cell. E) when small DNAs are converted into RNA by enzymes.
A
The lac repressor A) binds to the operator and prevents transcription. B) binds to the CAP site and prevents transcription. C) binds to the CAP site and facilitates transcription. D) binds to the operator and facilitates transcription.
A
The most efficient control of eukaryotic gene expression is achieved at the level of A) transcription initiation. B) post-translation. C) post-transcription. D) replication. E) translation initiation.
A
The protein ________ acts as an endonuclease in the first step of RNA interference. A) dicer B) sizer C) interferon D) vader E) phaser
A
The trp operon consists of ________ genes that encode tryptophan biosynthesis enzymes. A) five B) three C) two D) four E) one
A
Which of the following statements about enhancers is TRUE? A) Enhancers are sequences to which activators bind. B) Enhancers are sequences to which activators bind and they are found in the promoter of a gene. C) Enhancers are found in the promoter of a gene. D) Enhancers are found in the promoter of a gene, and they are only found in certain chromosomal locations. E) Enhancers are only found in certain chromosomal locations.
A
The lac operon is designed for self-preservation in a variety of environments. For each condition, determine whether the enzyme beta-galactosidase is made only when lactose is present, when lactose is present or absent, or if it is never made. Assume that glucose is absent from the environment. CHOOSE ALL: Expression when lactose is present or absent A) Operator (lacO) is mutated B) lacI- mutant with an F' factor carrying lacI+l C) Wild-type E. coli D) Operator (lacO) is mutated, but with an F' factor carrying lacO+ alone E) lacI- mutant F) Promoter is mutated G) Mutation of CAP H) lac Y mutant
A D E
How is it possible for a single gene to encode more than one polypeptide? A) It is not possible; this violates the "one gene - one enzyme" hypothesis. B) Introns can be removed from pre-mRNA in different combinations. C) mRNA bases can be rearranged in a modular fashion. D) A single transcription factor can regulate many genes. E) The exons in DNA can undergo a shuffling process during S phase.
B
Which region associated with the lac operon is not involved in the binding of RNA polymerase? A) lacO B) lacZ Correct C) CAP binding site
B
The lac operon is designed for self-preservation in a variety of environments. For each condition, determine whether the enzyme beta-galactosidase is made only when lactose is present, when lactose is present or absent, or if it is never made. Assume that glucose is absent from the environment. CHOOSE ALL: Expression only when lactose is present A) Operator (lacO) is mutated B) lacI- mutant with an F' factor carrying lacI+l C) Wild-type E. coli D) Operator (lacO) is mutated, but with an F' factor carrying lacO+ alone E) lacI- mutant F) Promoter is mutated G) Mutation of CAP H) lac Y mutant
B C H
How could drug developers use RNA interference in a medical application? A) They could increase the production of a protein that was under expressed. B) They could activate a protein that was failing to activate under normal conditions. C) They could stop the production of a defective protein. D) They could replace a defective protein with a healthy one.
C
In the absence of tryptophan, the trp repressor is A) active and cannot bind to the operator. B) inactive and can bind to the operator. C) inactive and cannot bind to the operator. D) active and can bind to the operator. E) inactive and cannot bind to the promoter.
C
RNA interference is stimulated in the presence of ________ in the cell. A) double-stranded DNA B) single-stranded DNA C) double-stranded RNA D) single-stranded RNA E) proteins
C
What would probably NOT increase the accessibility of the DNA for gene transcription? A) Enhancer proteins B) All of these will probably increase accessibility of the DNA C) Methylation of DNA D) Acetylation of histone tails E) Chromatin remodeling complexes
C
When in a complex with ________, the CAP protein binds to the CAP site and ________ the expression of the lac operon. A) glucose ; switches on B) lactose ; switches on C) cAMP ; switches on D) cAMP ; switches off E) glucose ; switches off
C
Determine whether each described change to chromatin structure would increase or decrease gene expression. CHOOSE ALL: Increase in gene expression A) Increase in compaction of histones B) Removal of acetyl groups from histone tails C) Decrease in compaction of histones D) Acetylation of histone tails E) Removal of histones from a region
C D E
A mutation in which regions of DNA could result in over-expression of ferritin? A) The IRP gene B) The IRE region of the ferritin gene C) The translated region of the ferritin gene D) The IRP gene or the IRE region of the ferritin gene E) The IRE region or the translated region of the ferritin gene
D
Cancer results from cells that divide when they should not. A hallmark of cancer is high levels of DNA methylation in cell genomes. Methylation of which genes is MOST likely to lead to cancerous cell formation? A) Genes that promote angiogenesis (formation of blood vessels) B) Genes that promote ATP production C) Genes that produce transcription factors D) Genes that prevent cell division E) Genes that promote cell division
D
In both the lac and trp operons of E. coli, a repressor binds to an operator to block transcription. Identify the most accurate description of these operons. A) The operator is a small molecule that binds the repressor (as a co-repressor). B) The trp operon is inducible while the lac operon is repressible. C) Both operons are considered inducible. D) The trp operon is repressible while the lac operon is inducible. D) Both operons are considered repressible.
D
RNA Polymerase II by itself does not have a strong affinity for binding DNA. Select the explanation that describes why cells do not need for RNA polymerase II to have a strong affinity for binding DNA for transcription to occur. A) RNA Polymerase II always works in tandem with RNA Polymerase I or III so that it is not required to have a strong affinity for binding to DNA. B) Natural selection has not yet had time to work sufficiently to produce an RNA Polymerase that has a strong affinity for binding DNA. C) RNA Polymerase II binds to the sigma factor, which facilitates its binding to DNA. D) The requirement of general transcription factors to bind RNA polymerase II to the DNA molecule gives the cell more precise control over transcription. E) RNA Polymerase II tightly binds to RNA, it is not required to bind to DNA to properly carry out its functions.
D
The lactose (lac) operon of E. coli is under both positive and negative control. How is the lac operon affected by positive control? A) Cyclic AMP (cAMP) binds directly to the lac promoter. B) The Lac Repressor binds to the operator when lactose is present. C) Lactose binds to the operator of the lac operon. D) The CAP protein binds near the promoter in the presence of cAMP. E) The presence of glucose stimulates transcription of the lac operon.
D
What protein would not interact with a coactivator? A) multiple activators simultaneously B) activators C) All of these would interact with the coactivators D) repressors E) basal transcription factors
D
Why does the concentration of glucose have an effect on the transcription of the lac operon? A) Glucose is an important cell signaling molecule. B) All of these are true C) The lac operon functions to metabolize glucose, lactose, and other small sugars. D) Glucose is the preferred sugar for the bacteria. If it is present, lactose metabolism is suppressed. E) Glucose is a precursor of lactose.
D
A regulatory element that can function from a large distance (e.g. tens of thousands of base pairs) from a promoter is called A) a repressor. B) a histone. C) an inducer. D) a core promoter. E) an enhancer.
E
Evaluate the statements below and determine which is the BEST reason that bacterial cells use operons and polycistronic RNA. A) Bacterial cells have a short life span, and transcribing single genes will take too long. B) Bacterial cells have small genomes that cannot accommodate large numbers of regulatory regions. C) Bacterial genes are very short, so RNA that is not polycistronic might be mistaken for fragments that should be digested. D) Operons are more stable than structural genes that are located singly on a chromosome. E) Initiation of transcription of all genes in a biochemical pathway is regulated simultaneously.
E
The lac operon is expressed when A) glucose is high and lactose is absent. B) glucose is low and lactose is absent. C) glucose is low, regardless of the presence or absence of lactose. D) glucose is high and lactose is present. E) glucose is low and lactose is present.
E
Which of the following statement(s) about basal transcription factors is(are) TRUE? A) They can decrease the rate of transcription by themselves. B) They cannot increase the rate of transcription by themselves. C) 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. E) They are essential for transcription and they cannot increase the rate of transcription by themselves.
E
Which of the following statements about basal transcription factors is TRUE? A) they can decrease the rate of transcription by themselves B) they are essential for transcription C) 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 cannot increase the rate of transcription by themselves E) they are essential for transcription and they cannot increase the rate of transcription by themselves
E
Which of the following statements is NOT true of the regulation of ferritin production? A) Ferritin mRNA has secondary structure. B) Ferritin translation is regulated by the concentration of iron in the cytosol. C) Ferretin can only be translated if IRP dissociates from the mRNA. D) Ferritin mRNA is transcribed, but translation is delayed. E) IRP aids in ribosomal binding to ferritin mRNA.
E
TRUE or FALSE: 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 execute a specific program of development (e.g. to become a blood cell or immune cell).
TRUE
TRUE or FALSE: 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 stop synthesis of a cellular component when there is enough available in the cell.
TRUE
DNA is associated with proteins to form _____.
chromatin
The idea that gene regulation involves multiple factors is called_____.
combinatorial control
Addition of (-COCH₃) groups to histone amino terminal tails results in a/an _____ in gene expression.
increase
Modification of bases in DNA, usually resulting in inhibition of transcription, results from _____.
methylation
An activator can increase transcription by attracting a _____ to the region.
histone acetyltransferase
Assembly of basal transcription factors begins at the ________ sequence in the promoter. A) TATA B) AATT C) ACGT D) GAGA E) GGCC
A
Distinguish between the characteristics associated with each of the four types of gene regulation. Post-transcriptional A) The correct removal of introns of a pre-mRNA is prevented. B) The rate of degradation of a protein is increased C) Stability of an mRNA is regulated. D) An activator binds to an enhancer. E) A repressor binds near a promoter F) A phosphate group is added to a protein, making it inactive. G) The ability of an mRNA to bind to ribosomes is changed. H) Export of an mRNA to the cytoplasm is blocked. I) The 5' end of an mRNA forms a shape that blocks translation.
A C H
How is the lac operon affected by negative control? A) RNA polymerase must bind with allolactose to start transcription. B) The Lac Repressor binds to the operator in the absence of lactose. C) Beta-galactosidase cleaves the Lac Repressor into two parts. D) Allolactose binds to the promoter and prevents transcription. E) Allolactose causes a conformational change in a protein to start transcription.
B
Removal of acetyl groups from histones results in a/an _____ in gene expression.
decrease
A protein that binds to DNA and blocks activation of a small number of genes is a/an _____.
repressor
A protein that binds to DNA and activates transcription of some genes is a/an _____.
activator
What level of regulation do eukaryotes possess that prokaryotes do not? A) initiation of transcription B) degradation of mRNA C) initiation of translation D) rate of elongation during translation E) transport of RNA out of the nucleus
E
In the presence of tryptophan, tryptophan binds to the A) trp genes. B) RNA polymerase. C) trp repressor. D) promoter. E) operator.
C
The assembly of transcription factors begins A) upstream from the translation start site. B) downstream from the translation stop site. C) upstream from the transcription start site. D) downstream from the transcription start site. E) downstream from the translation start site.
C
The lac repressor binds to what site within the lac operon? A) lacZ B) lacP C) lacO D) lacl E) lacA
C
Transcription is carried out by the enzyme A) reverse transcriptase. B) topoisomerase. C) RNAse. D) RNA polymerase. E) DNA polymerase.
D
Genes that encode proteins are first transcribed to mRNA, and then are translated into protein. What is the MOST important factor determining the control of gene expression? A) The level of transcription (when a gene is transcribed to mRNA) B) Nascent polypeptide folding into a protein C) The stability of the mRNA (how long a molecule lasts in the cytoplasm) D) Initiation of translation E) Availability of free ribonucleotides for transcription
A
In the experiment by Jacob, Monod, and Pardee, it was demonstrated that bacteria with a mutant lacl- gene that were transformed with a plasmid encoding a functional lacl gene and lac operon were restored to normal repression of the lac operon in the absence of lactose. If their data showed that merozygote strains not receiving lactose still produced β-galactosidase, what might their conclusions have been? A) The lacl gene is a cis-acting element B) The lacl allele is a trans-acting inducer C) The lacl gene exhibits a trans effect D) The lacl gene is a trans-acting repressor E) The lacl allele (wild type) is dominant to the lacl- (mutant) allele
NOT B C E
The trp operon of E. coli controls expression of five enzymes that are involved in the biosynthesis of the amino acid tryptophan. A trp repressor protein (trpR) binds to the trp operator to prevent transcription when tryptophan is present. When would the tryptophan synthesis enzymes be made if the trpR gene was mutated? A) The enzymes would be made in the presence or absence of tryptophan. B) The enzymes would never be made because the repressor would not bind DNA. C) Only when tryptophan was absent. D) Only when tryptophan was present. E) In the presence of lactose.
A
If lacO were mutated, what effect would this have on lactose metabolism? A) RNA polymerase would not properly bind to the promoter, and the lac operon would be under expressed. B) The repressor would not properly bind to the operator, and the lac operon would be over expressed. C) The repressor protein would not function properly, and the lac operon would be over expressed. D) The repressor would not properly bind to the operator, and the lac operon would be under expressed.
B
How could an activator influence gene expression at a promoter far away from the place that it binds DNA? A) Histone proteins are modified to create a closed conformation. B) Ribosomes are recruited to the promoter by the activator. C) The activator methylates the DNA and this causes long-distance activation. D) The activator directly binds to RNA polymerase, which then skips over a large region of DNA to start transcription. E) A Mediator protein is stimulated by the bound activator, and then the Mediator stimulates transcription.
E
Function of _____ can be modulated by binding of small effector molecules, protein-protein interactions, or covalent modifications.
activators and repressors
A _____ is composed of DNA wrapped around an octamer of histone proteins.
nucleosome
When a transcription factor interacts with DNA, A) it forms noncovalent bonds with functional groups on the nitrogenous bases. B) histones must be present in the promoter. C) covalent bonds are formed so that the factor cannot be removed. D) it cannot recognize specific bases in the DNA. E) it interacts only with the sugar-phosphate backbone of the DNA.
A
Distinguish between the characteristics associated with each of the four types of gene regulation. Post-translational A) The correct removal of introns of a pre-mRNA is prevented. B) The rate of degradation of a protein is increased C) Stability of an mRNA is regulated. D) An activator binds to an enhancer. E) A repressor binds near a promoter F) A phosphate group is added to a protein, making it inactive. G) The ability of an mRNA to bind to ribosomes is changed. H) Export of an mRNA to the cytoplasm is blocked. I) The 5' end of an mRNA forms a shape that blocks translation.
B F
Small effector molecules A) directly aid the binding of RNA polymerase to the promoter region. Incorrect B) are usually enzymes that regulate a key step in a biological pathway. C) are often end products or key metabolites of a metabolic pathway. D) are themselves inhibitor or activator proteins. E) bind directly to the DNA to enhance or repress transcription.
C
TRUE or FALSE: 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 synthesize enzymes to metabolize a particular nutrient.
TRUE
Determine whether each described change to chromatin structure would increase or decrease gene expression. CHOOSE ALL: Decrease in gene expression A) Increase in compaction of histones B) Removal of acetyl groups from histone tails C) Decrease in compaction of histones D) Acetylation of histone tails E) Removal of histones from a region
A B
Small RNA gene regulation A) form secondary shapes that cause interference with protein function by binding to enzyme active sites. B) bind together to form stem-loop structures that are recognized by regulatory proteins. C) can aggregate together to form long anti-sense mRNAs that can bind to a mRNA to block its activity. D) influence the splicing of an mRNA from its primary transcript. E) bind to an mRNA, resulting in destruction of the mRNA or blockage of translation.
E
What is the MOST important reason a cell would have translational control over the regulation of gene expression? A) At the translational level, protein synthesis can be turned on and off quickly to respond to the needs of the cell. B) Regulation at the translational level is the most energetically efficient for the cell. C) At the translational level, mRNA can be degraded quickly to lower the protein concentration in the cytoplasm. D) Cells can best regulate the concentration of protein at the translational level. E) Regulation at the translational level can affect the differentiation of future generations of cells.
A
Select the BEST description of the complexity of eukaryotic gene expression as compared to prokaryotic gene expression. A) Eukaryotic mRNA molecules usually code for a single structural gene while prokaryotic mRNA are generally polycistronic. B) Eukaryotic transcription is usually influenced by many transcription factors while prokaryotic transcription is usually influenced by only a few transcription factors. C) Eukaryotic transcription involves general transcription factors while prokaryotic transcription involves an operator. D) Eukaryotes have much larger genomes than prokaryotes. E) Eukaryotes have linear chromosomes while prokaryotes have circular chromosomes.
B
TRUE or FALSE: 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 make additional cells of the same type in response to a demand.
TRUE
Distinguish between the characteristics associated with each of the four types of gene regulation. Transcriptional A) The correct removal of introns of a pre-mRNA is prevented. B) The rate of degradation of a protein is increased C) Stability of an mRNA is regulated. D) An activator binds to an enhancer. E) A repressor binds near a promoter F) A phosphate group is added to a protein, making it inactive. G) The ability of an mRNA to bind to ribosomes is changed. H) Export of an mRNA to the cytoplasm is blocked. I) The 5' end of an mRNA forms a shape that blocks translation.
D E
Which of the 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 necessary because RNA polymerase cannot efficiently bind to the DNA by itself. B) The complexity is a result of multiple gene duplication events. C) The complexity allows more than one protein to be transcribed by a single RNA polymerase. D) The complexity allows specific control over the timing and quantity of the protein produced. E) The complexity ensures that a single mutation cannot effect the function of the protein.
D
What is a major disadvantage to a bacterial cell of having an operon? A) If there is a mutation in one of the structural genes, none of the proteins will be functional. B) The cell is unable to regulate the transcription of the genes in the operon. C) The cell must transcribe multiple proteins at one time. D) The cell must regulate the transcription of all of the genes in the operon simultaneously. E) If there is a mutation in a regulatory region, none of the proteins will be synthesized.
E
Suppose that a large double-stranded RNA (dsRNA) that corresponds to an enzyme's mRNA sequence was injected into a eukaryotic cell. This dsRNA is cleaved by Dicer into smaller pieces. Normally, the enzyme encoded by the mRNA is being made continuously. What would likely happen to the enzyme's activity? A) Activity of the enzyme would be stimulated by the presence of the small RNA fragments. B) Some of the smaller pieces could act as siRNAs and cause the endogenous enzyme's mRNA to be degraded, resulting in loss of the enzyme. C) The smaller pieces could bind directly to the enzyme, causing it to stop functioning. D) The RNA fragments would not be expected to have any effect on the ability of the cell to produce the enzyme. E) The small RNAs could get translated by the ribosome, and the resulting protein fragments could assemble into the enzyme. Hence, the enzyme activity will increase.
B
How does the cell recognize that lactose needs to be metabolized? A) Lactose stimulates a transcription factor that activates transcription of the lac operon. B) Lactose directly activates the transcription of the lac operon. C) Lactose is converted into allolactose, which inhibits the lac repressor. D) Lactose stimulates the production of cAMP, which activates kinases that activate transcription of the lac operon. E) Lactose is converted into beta-galactosidase, which inhibits the lac repressor.
C
In the absence of lactose, the lac repressor is A) active and can bind to the operator. B) inactive and can bind to the operator. C) active and cannot bind to the operator. D) inactive and cannot bind to the operator. E) inactive and cannot bind to the promoter.
A
At which of the following level(s) can gene expression be regulated in eukaryotes? A) passage of mRNA through the nuclear membrane, destruction of the mRNA, and rate of protein synthesis B) destruction of the mRNA C) passage of mRNA through the nuclear membrane and destruction of the mRNA D) passage of mRNA through the nuclear membrane E) rate of protein synthesis
A
When both glucose and lactose are present, A) RNA polymerase is able to bind to the operator so transcription occurs. B) transcription is turned off. C) cyclic AMP is high so transcription occurs. D) the lac repressor binds with the lactose and transcription occurs.
B
When glucose is present A) high; CAP does not bind to the activator binding site, and transcription of the operon is turned on. B) low; CAP does not bind to the activator binding site, and transcription ofthe operon is turned off. C) low; CAP binds to the site activator binding site, and transcription of the operon is turned on. D) high; the catabolite activator protein (CAP) binds to the activator binding site, and transcription of the operon is turned on.
B
Distinguish between the characteristics associated with each of the four types of gene regulation. Translational A) The correct removal of introns of a pre-mRNA is prevented. B) The rate of degradation of a protein is increased C) Stability of an mRNA is regulated. D) An activator binds to an enhancer. E) A repressor binds near a promoter F) A phosphate group is added to a protein, making it inactive. G) The ability of an mRNA to bind to ribosomes is changed. H) Export of an mRNA to the cytoplasm is blocked. I) The 5' end of an mRNA forms a shape that blocks translation.
G I
How does glucose effect 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, it stimulates the production of cAMP, which binds to and deactivates the repressor, preventing it from binding to the DNA. C) When glucose levels are low, glucose binds to and activates the repressor, causing it to associate with the DNA. D) 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. E) 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.
NOT A B C E NOT A B D
RNA intereference is a mechanism for silencing gene expression at the A) level of transcription. B) post-transcriptional but pre-translational level. C) level of translation. D) level of replication. E) post-translational level.
B
RNA polymerase binds to the A) enhancer. B) promoter. C) terminator. D) operator. E) regulator.
B
TFIID binds to A) DNA. B) DNA, activators, and RNA Polymerase II. C) RNA Polymerase II. D) activators. E) DNA and RNA Polymerase II.
B
The lac repressor is inactivated by binding to which of the following? A) glucose B) allolactose C) betagalactosidase D) lactose E) transcription factors
B
Which statement represents the best explanation for why eukaryotes use basal, or general, transcription factors? A) They give the cell tight control over transcription. B) They interact with coactivators. C) Eukaryotes do not use the sigma factor. D) They allow RNA polymerase to locate the promoter. E) RNA polymerase cannot bind to the DNA without their aid.
A
What is the MOST important reason a cell exhibits tight transcriptional control over the regulation of gene expression? A) At the transcriptional level, mRNA can be degraded quickly to lower their concentration in the cytoplasm. B) Regulation at the transcriptional level is energetically efficient for the cell. C) At the transcriptional level, protein synthesis can be turned on and off quickly to respond to the needs of the cell D) Cells can only regulate the concentration of protein at the transcriptional level. E) Regulation at the transcriptional level can affect the differentiation of future generations of cells.
B
Combinatorial control of gene expression does not involve A) chromatin remodeling. B) Mediator. C) polycistronic RNA. D) general transcription factors. E) Enhancers and repressors.
C
Which of the following is not part of the lac operon? A) lacO B) lacZ C) lacl D) lacP E) lacA
C
Which of the following statements about chromatin is TRUE? A) Covalent modification of histone tails always leads to a decrease in transcription. B) Nucleosomes that are acetylated are associated with DNA that is inaccessible to RNA Polymerase and other transcription factors. C) Modifying the accessibility of chromatin leads to complex regulation of eukaryotic gene expression. D) Covalent modification of histone tails always leads to an increase in transcription. E) Chromatin in an open conformation is bound to many nucleosomes.
C
How did Jacob, Monod, and Pardee measure the amount of β-galactosidase present in their experimental cells. A) The amount of β-galactosidase was inferred by the relative pH of the solutions. Solutions with high amounts of β-galactosidase turn yellow in the presence of the pH indicator and solutions without β-galactosidase are colorless. B) They used a β-galactosidase meter that automatically generated a concentration of β-galactosidase when the sensor was placed in a solution C) β-galactosidase exhibits a yellow color and the amount of color was measured with a spectrophotometer D) β-galactosidase was assayed by adding a molecule similar to lactose. When the β-galactosidase acts on this molecule, it results in a yellow compound, and the amount of yellow color was measured with a spectrophotometer E) β-galactosidase was assayed by adding lactose, which turns yellow when acted upon by β-galactosidase. The amount of yellow color was measured with a spectrophotometer.
D
It is often desirable to express eukaryotic genes in bacteria, which can make a protein of interest quickly and cheaply. What is TRUE about this kind of genetic transformation? A) Only the transcribed region of the gene should be incorporated into the bacterial genome. No promoter is necessary to transcribe a transformed gene. B) The expressed gene and the gene for RNA Polymerase II must both be incorporated into the bacterial genome. C) Only polycistronic genes are capable of being expressed in a bacteria. D) The expressed gene must be incorporated into the bacterial chromosome, but its promoter region should be replaced with a bacterial promoter. E) The expressed gene and the genes for all of its regulatory elements must be incorporated into the bacterial chromosome.
D
TRUE or FALSE: 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 synthesize mRNA for every gene in the genome at all times.
FALSE
The nematode C. elegans has approximately 19,000 genes, while humans have 25,000. Although the number of genes is similar, humans can make more than 4x as many proteins as C. elegans. What is the most plausible explanation for this phenomenon? A) Genes in humans are much larger than those of C. elegans. B) Human proteins are modified post-translationally by changing amino acid side chains. C) In humans, genes can be transcribed using either strand of DNA as a template. D) In humans, more pre-RNAs can be alternatively spliced to generate different mRNAs. E) The C. elegans genome is much smaller in size, so not as many proteins are made.
D
What is NOT a mechanism used by enhancers and repressors to affect gene expression? A) They aid or inhibit the binding of the general transcription factors to the promoter. B) They act in a combinatorial fashion to elicit complex responses. C) They make DNA more or less accessible to RNA polymerase and other proteins associated with transcription. D) All of these are mechanisms used by enhancers or repressors to affect gene expression. E) The aid or inhibit the binding of RNA polymerase to the promoter.
D
Which of the following statements best describes the consequence of this mutation on expression of a transcriptional target gene? A) The gene will be expressed as normal. B) The gene will not be expressed. C) The gene will be over expressed. D) The gene will be expressed constitutively. E) The gene will be expressed, but in less than optimal quantities.
E
The lac operon is designed for self-preservation in a variety of environments. For each condition, determine whether the enzyme beta-galactosidase is made only when lactose is present, when lactose is present or absent, or if it is never made. Assume that glucose is absent from the environment. CHOOSE ALL: No expression even when lactose is present A) Operator (lacO) is mutated B) lacI- mutant with an F' factor carrying lacI+l C) Wild-type E. coli D) Operator (lacO) is mutated, but with an F' factor carrying lacO+ alone E) lacI- mutant F) Promoter is mutated G) Mutation of CAP H) lac Y mutant
F G
TRUE or FALSE: 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 keep a gene product available under all conditions.
FALSE