Ch. 18 Launchpad

Among the exons in a primary RNA transcript, two are subject to alternative splicing. In RNA processing, one or the other or neither or both regions may be excised from the primary transcript as introns. How many different amino acid sequences could this transcript encode? 2 4 5 1 3

4

Refer to the drawing of mRNA shown. Click to view full size. Choose the letter that best fits the description. The 5' UTR corresponds to: a. region D. b. region C. c. region E. d. region A. e. region B.

e

All ApT sites located near the promoter region of protein coding genes are methylated. true false

false

Histone modification occurs only during early development. true false

false

MicroRNA (miRNA) can affect gene expression in three ways: by causing chromatin remodeling, by causing RNA degradation, or by causing translation inhibition. In some tissues, Gene X is regulated by the expression of an miRNA. In other tissues, the miRNA affecting Gene X is not expressed. Analysis of the gene's RNA and protein products show the following: How must the miRNA be affecting the expression of Gene X? a. The miRNA is causing degradation of the Gene X mRNA. b. The miRNA is inhibiting translation of the Gene X mRNA. c. The miRNA is affecting the chromatin structure of Gene X.

a

MicroRNA (miRNA) can affect gene expression in three ways: by causing chromatin remodeling, by causing RNA degradation, or by causing translation inhibition. In some tissues, Gene X is regulated by the expression of an miRNA. In other tissues, the miRNA affecting Gene X is not expressed. Analysis of the gene's RNA and protein products show the following: How must the miRNA be affecting the expression of Gene X? a. The miRNA is inhibiting translation of the Gene X mRNA. b. The miRNA is causing degradation of the Gene X mRNA. c. The miRNA is affecting the chromatin structure of Gene X.

a

One regulatory step in the process of gene expression and synthesis of proteins is the actual modification of proteins themselves, which is called: a. posttranslational modification. b. chromatin remodeling. c. alternative splicing. d. translational inhibition. e. tissue-specific editing.

a

Refer to the drawing of mRNA shown. Click to view full size. Choose the letter that best fits the description. The protein-coding region corresponds to: a. region C. b. region E. c. region D. d. region A. e. region B.

a

What happens when the Xist gene from an X chromosome is inserted into an autosome? a. The autosome with Xist is inactivated like an X chromosome. b. Gene activity in the autosome remains normal. c. Both the autosome and its homologous chromosome are inactivated. d. The autosome with Xist is inactivated in half the cells, and the homologous autosome without Xist is inactivated in the other half.

a

What would be the consequence of a mutation in the lacI repressor gene that produces a repressor protein that is able to bind the operator, but is not able to bind allolactose? a. The lacZ and lacY genes would not be expressed even when lactose is present. b. The lacZ and lacY genes would be expressed when lactose is present. c. The lacZ and lacYgenes would be expressed when lactose is absent.

a

When a small regulatory RNA is processed from an RNA transcript with a stem-and-loop structure, the RNA fragments used in regulation come from: a. the stem. b. the loop. c. both the stem and the loop. d. the junction between the stem and the loop.

a

MicroRNA (miRNA) can affect gene expression in three ways: by causing chromatin remodeling, by causing RNA degradation, or by causing translation inhibition. In some tissues, Gene X is regulated by the expression of an miRNA. In other tissues, the miRNA affecting Gene X is not expressed. Analysis of the gene's RNA and protein products show the following: a. The miRNA is affecting the chromatin structure of Gene X. b. The miRNA is inhibiting translation of the Gene X mRNA. c. The miRNA is causing degradation of the Gene X mRNA.

b

MicroRNA is a type of: a. splicing RNA. b. regulatory RNA. c. transfer RNA. d. messenger RNA. e. ribosomal RNA.

b

Prion protein (PrP) can cause mad cow disease when it folds improperly and forms protein aggregates. Which answer option could cause misfolding of PrP? a. changes that affect the Poly(A) tail of the PrP mRNA b. changes affecting chaperone proteins that bind to PrP c. changes affecting the 5′ cap on the PrP mRNA d. changes in expression of miRNAs that pair with PrP mRNAs e. changes affecting modification of histone tails of chromatin containing the PrP gene

b

Which condition would cause constitutive expression of lacZ and lacY? a. mutations in lacI that prevent the repressor from binding to lactose b. All of these choices are correct. c. mutations in lacO that prevent it from binding to the repressor d. high levels of lactose and low levels of glucose

b

A mutation in Gene X is caused by a small deletion that reduces the size of the mRNA. This mutation does not disrupt translation, but causes the protein to be produced in the wrong location in the cell. Which region of the mRNA must be affected by this mutation? a. the poly(A) tail b. the 3' UTR c. the 5' UTR d. the ORF e. the 5' cap

c

A particular human gene is expressed in both the heart and the lung. However, analysis of the products of this gene shows that both the mRNA and the protein encoded by this gene are larger in lung tissue than in heart tissue. Which answer option could have caused these differences in protein and mRNA between the heart and lung? a. methylation of CpG islands in the promoter of the gene in the heart but not the lung b. RNA editing that occurs in the heart but not the lung c. RNA splicing that includes particular exons in the gene's mRNA in the lung but not the heart d. binding of transcription factors to silencer sequences of the gene in the heart but not the lung

c

Anhidrosis Ectodermal Dysplasia is caused by a single gene mutation that affects the ability of sweat glands to function properly. Human males affected by this mutation cannot produce sweat properly anywhere on their body, whereas females with this condition are affected in a mosaic pattern in which some patches of skin cannot produce sweat while other areas can. Which answer option could account for this mosaicism in females but not males? a. Histone tails are modified one way in females and another way in males. b. The primary transcript of the gene causing this disorder undergoes alternative processing and produces different mRNAs in females and males. c. The gene causing this disorder is located on the X chromosome. d. CpG islands in the promoter of the gene causing this disorder are methylated in males but not in females.

c

MicroRNA (miRNA) can affect gene expression in three ways: by causing chromatin remodeling, by causing RNA degradation, or by causing translation inhibition. In some tissues, Gene X is regulated by the expression of an miRNA. In other tissues, the miRNA affecting Gene X is not expressed. Analysis of the gene's RNA and protein products show the following: a. The miRNA is affecting the chromatin structure of Gene X. b. The miRNA is inhibiting translation of the Gene X mRNA. c. The miRNA is causing degradation of the Gene X mRNA.

c

Patau Syndrome is a severe birth defect caused by an extra copy of chromosome 13 (trisomy 13). Which procedure, if done early in development, could counteract the effect of having an extra copy of chromosome 13 and potentially be a treatment for Patau Syndrome? a. alternative splicing of primary transcripts from genes located on all three copies of chromosome 13 b. binding of transcription factors to enhancer sequences on one of the three copies of chromosome 13 c. insertion of a copy of the Xist gene onto one of the three copies of chromosome 13 d. de-methylation of the CpG islands on one of the three copies of chromosome 13

c

Transcription is repressed when the cytosines within CpG islands in genes' promoters are methylated. Which answer option could account for this effect on gene expression? a. Methylated cytosines could stimulate the expression of the Xist gene, causing it to bind to the chromosome and spread outward from the CpG island. b. Methylated cytosines cause modification to histone tails that induce the uncoiling of chromatin, providing access to transcription factors. c. Methylated cytosines bind to enzymes that cause the removal of acetyl groups from histones, causing chromatin to coil more tightly. d. Methylated cytosines enhance the binding of transcription factors to enhancer sequences in the gene's promoter.

c

Refer to the drawing of mRNA shown. Click to view full size. Choose the letter that best fits the description A messenger RNA lacking region E is likely to be: a. retained in the nucleus. b. exported outside the cell. c. None of the other choices are correct. d. exceptionally resistant to degradation.

c, (exceptionally sensitive to degration )

In bacteriophage that can undergo lysis or lysogeny, which protein acts as a positive regulator of transcription of some bacteriophage genes and as a negative regulator of transcription of other bacteriophage genes? cII cI cro

cI

A particular human gene is expressed in both the heart and the lung. However, analysis of the products of this gene shows that both the mRNA and the protein encoded by this gene are larger in lung tissue than in heart tissue. Which answer option could have caused these differences in protein and mRNA between the heart and lung? a. RNA splicing that includes particular exons in the gene's mRNA in the lung but not the heart b. RNA editing that occurs in the heart but not the lung c. methylation of CpG islands in the promoter of the gene in the heart but not the lung d. binding of transcription factors to silencer sequences of the gene in the heart but not the lung

a

A virus that infects bacteria is called a: a. bacteriophage. b. lysogenic virus. c. microphage. d. lytic virus. e. temperate virus.

a

Consider the figure shown. Which type of mutation could block the lysogenic pathway and cause a phage to follow the lytic pathway? a. a mutation that blocks the function of the PR promoter b. a mutation that blocks the function of the PL promoter c. a mutation that blocks expression of the cro gene d. All of these choices are correct. e. a mutation that enhances the binding of the cI protein to OL

a

In a bacteriophage that undergoes lysogeny, genes for the lytic pathway are: a. repressed. b. induced. c. transcribed but not translated. d. translated but not functional.

a

In prokaryotes: a. the translation of an mRNA can begin even before transcription is completed. b. DNA is packaged into nucleosomes. c. the primary RNA transcript needs a "cap" at the 5' end for the initiation of translation. d. the primary transcript undergoes three-step processing.

a

In prokaryotes: a. the translation of an mRNA can begin even before transcription is completed. b. the primary RNA transcript needs a "cap" at the 5' end for the initiation of translation. c. the DNA is packaged into nucleosomes. d. translation of an mRNA cannot begin until transcription is completed.

a

Which answer choice is an accurate description of events leading to the lytic pathway following viral infection in a bacterium? a. When bacterial cells are grown in favorable conditions, proteases degrade cII, cro represses cI transcription, which leads to the expression of all genes needed for synthesis of phage components and lysis. b. Accumulation of cII protein is the most important contributor to lytic pathway initiation. c. The cro protein initiates transcription from PM so that the cl protein is expressed which leads to the transcription of all genes needed for synthesis of phage components and lysis. d. When bacterial cells are grown in favorable conditions, strong protease activity rapidly degrades cro, leading to the lytic path.

a

Which answer choice occurs during RNA processing? a. the addition of a nucleotide cap to the 5' end and a poly(A) tail to the 3' end of the newly transcribed RNA b. the removal of poly(A) tails from the primary transcript c. the removal of all exons during RNA splicing d. the removal of a nucleotide cap to the 5' end and a poly(A) tail to the 3' end of the newly transcribed RNA

a

Which condition would cause constitutive expression of lacZ and lacY? a. All of these choices are correct. b. mutations in lacO that prevent it from binding to the repressor c. high levels of lactose and low levels of glucose d. mutations in lacI that prevent the repressor from binding to lactose

a

Which statement about regulation of translation is correct? a. Translation initiation complexes recognize and bind to the 5' cap. b. The translation initiation complex scans for a TAC codon near the 5' cap. c. The 5' UTR sequence does not affect the efficiency of translation initiation. d. Regulation of translation does not depend on sequences in the 3' UTR or the poly(A) tail. e. One of the key variables for influencing efficient translation is the sequence of nucleotides flanking the first GUG codon.

a

Consider the figure shown. Which type of mutation could block the lysogenic pathway and cause a phage to follow the lytic pathway?

a mutation that blocks the function of the PR promoter

In RNA editing: a. enzymes change the base sequence of the primary transcript and therefore the protein for which it codes. b. different spliceosomes in different cells create different RNA sequences from the same primary transcript. c. a combination of spliceosomes and enzymes creates different primary RNA transcripts from the same DNA sequence. d. microRNAs in different cells create different primary RNA transcripts from the same DNA sequence. e. spliceosomes change the base sequence of the primary transcript and therefore the protein for which it codes.

a.

Anhidrosis Ectodermal Dysplasia is caused by a single gene mutation that affects the ability of sweat glands to function properly. Human males affected by this mutation cannot produce sweat properly anywhere on their body, whereas females with this condition are affected in a mosaic pattern in which some patches of skin cannot produce sweat while other areas can. Which answer option could account for this mosaicism in females but not males? a. The primary transcript of the gene causing this disorder undergoes alternative processing and produces different mRNAs in females and males. b. The gene causing this disorder is located on the X chromosome. c. CpG islands in the promoter of the gene causing this disorder are methylated in males but not in females. d. Histone tails are modified one way in females and another way in males.

b

Anhidrosis Ectodermal Dysplasia is caused by a single gene mutation that affects the ability of sweat glands to function properly. Human males affected by this mutation cannot produce sweat properly anywhere on their body, whereas females with this condition are affected in a mosaic pattern in which some patches of skin cannot produce sweat while other areas can. Which answer option could account for this mosaicism in females but not males? a. The primary transcript of the gene causing this disorder undergoes alternative processing and produces different mRNAs in females and males. b. The gene causing this disorder is located on the X chromosome. CpG islands in the promoter of the gene causing this disorder are methylated in males but not in females. c. Histone tails are modified one way in females and another way in males.

b

For the lactose operon, the CRP-cAMP is a(n): a. operator. b. activator. c. promoter. d. inducer. e. repressor.

b

In RNA editing: a. different spliceosomes in different cells create different RNA sequences from the same primary transcript. b. enzymes change the base sequence of the primary transcript and therefore the protein for which it codes. c. a combination of spliceosomes and enzymes creates different primary RNA transcripts from the same DNA sequence. d. microRNAs in different cells create different primary RNA transcripts from the same DNA sequence. e. spliceosomes change the base sequence of the primary transcript and therefore the protein for which it codes.

b

In humans and other mammals, dosage compensation is achieved by: a. females inactivating the paternal X chromosome in each cell. b. females randomly inactivating one X chromosome in each cell. c. males transcribing twice the normal amount of copies of X-chromosome genes. d. females decreasing transcription of both X chromosomes by half. e. females eliminating one X chromosome in each cell.

b

In prokaryotes: a. the primary transcript undergoes three-step processing. b. the translation of an mRNA can begin even before transcription is completed. c. the primary RNA transcript needs a "cap" at the 5' end for the initiation of translation. d. DNA is packaged into nucleosomes.

b

A particular human gene is expressed in both the heart and the lung. However, analysis of the products of this gene show that the protein encoded by this gene is larger in lung tissue than in heart tissue, even though the mRNAs in both of those tissues are the same size. Which answer option could have caused the size difference in the proteins, but not the mRNAs, between the heart and lung? a. methylation of CpG islands in the promoter of the gene in the heart but not the lung. b. binding of transcription factors to silencer sequences of the gene in the heart but not the lung. c. RNA splicing that includes particular exons in the gene's mRNA in the lung but not the heart d. RNA editing that occurs in the heart but not the lung

d

Active β-galactosidase enzyme is observed only in E. coli growing in the presence of lactose. One hypothesis is that the enzyme is always being produced but is produced in an unstable form that breaks down rapidly in the absence of lactose (hypothesis 1). A second hypothesis is that the enzyme is stable but is produced only in the presence of lactose (hypothesis 2). An experiment was performed to test these hypotheses. A culture of growing cells was exposed to lactose, which was later removed. The amount of β-galactosidase present in the culture during the course of the experiment was measured. The data are shown in the following graph. Which statement is a conclusion that can be obtained from these experimental data? a. The amount of β-galactosidase in the culture remained stable after lactose was removed, in support of hypothesis 1. b. Synthesis of β-galactosidase is turned on when lactose is added and turned off when lactose is removed, in support of hypothesis 1. c. The amount of β-galactosidase in the culture decreased rapidly after lactose was removed, in support of hypothesis 1. d. Synthesis of β-galactosidase is turned on when lactose is added and turned off when lactose is removed, in support of hypothesis 2. e. The amount of β-galactosidase in the culture decreased rapidly after lactose was removed, in support of hypothesis 2.

d

An operon is a: a. region of DNA consisting of the promoter and operator sequences needed to regulate one or more structural genes but does not include those coding sequences. b. region of DNA consisting of the operator and coding sequences for structural proteins, but not the promoter. c. gene coding for a repressor protein. d. region of DNA consisting of the promoter, the operator, and coding sequences for structural proteins. e. single molecule of RNA coding for more than one protein.

d

For the lactose operon, lactose is a(n): a. operator. b. repressor. c. promoter. d. inducer. e. activator.

d

Gene regulation by small regulatory RNAs in eukaryotes may have evolved originally as a: a. way to regulate the immune response. b. way to assist dosage compensation. c. way to regulate gene expression. d. defense against viruses and transposable elements. e. defense against mutations that may cause cancer.

d

MicroRNA is a type of: a. ribosomal RNA. b. transfer RNA. c. splicing RNA. d. regulatory RNA. e. messenger RNA

d

Refer to the drawing of mRNA shown. Click to view full size. Choose the letter that best fits the description. The 3' UTR corresponds to: a. region A. b. region B. c. region C. d. region D. e. region E.

d

Refer to the drawing of mRNA shown. Click to view full size. Choose the letter that best fits the description. Which structure is essential for translation initiation? a. region D b. region C c. region B d. region A e. region E

d

Small regulatory RNAs are incorporated into a protein complex known as: a. RAPD. b. REP. c. RIL. d. RISC.

d

The following are two genotypes of the lactose operon in E. coli:I. I+ P+ Oc Z+ Y+II. I- P+ O+ Z+ Y+ Do either of these genotypes produce β-galactosidase and permease in the absence of lactose? a. Neither produces β-galactosidase and permease. b. The first one does not produce β-galactosidase and permease; the second one does. c. The first one produces β-galactosidase and permease; the second one does not. d. Both produce β-galactosidase and permease.

d

The following are two genotypes of the lactose operon in E. coli:I. I+ P- Oc Z+ Y+II. I- P+ O+ Z+ Y+ Do either of these genotypes produce β-galactosidase and permease in the presence of lactose? a. The first one produces β-galactosidase and permease, the second one does not. b. Neither produces β-galactosidase and permease. c. Both produce β-galactosidase and permease. d. The first one does not produce β-galactosidase and permease, the second one does.

d

Transcription is repressed when the cytosines within CpG islands in genes' promoters are methylated. Which answer option could account for this effect on gene expression? a. Methylated cytosines could stimulate the expression of the Xist gene, causing it to bind to the chromosome and spread outward from the CpG island. b. Methylated cytosines enhance the binding of transcription factors to enhancer sequences in the gene's promoter. c. Methylated cytosines cause modification to histone tails that induce the uncoiling of chromatin, providing access to transcription factors. d. Methylated cytosines bind to enzymes that cause the removal of acetyl groups from histones, causing chromatin to coil more tightly.

d

Which answer choice is an accurate description of events leading to the lysogenic pathway following viral infection in a bacterium? a. The cro protein initiates transcription from PM so that the cl protein is expressed, which leads to the transcription of all genes needed for the initiation of the lysogeny. b. Reduced protease activity due to poor conditions allows cI to accumulate, which then stimulates of cro which in turn leads to the transcription of all genes needed for synthesis of phage components and lysogeny. c. When bacterial cells are grown in favorable conditions, proteases degrade cII, cro represses cI transcription, which leads to lysogenic pathway. d. Accumulation of cII protein is the most important contributor to lysogeny.

d

Which answer option accurately describes events in the movement of mRNA from the nucleus to the cytoplasm? a. Primary transcripts are processed to mRNA in the cytoplasm after leaving the nucleus. b. Once the mRNA is in the cytoplasm, there are no ways to regulate its stability and translation. c. Processed mRNA transcripts diffuse passively down their concentration gradient across the nuclear membrane. d. Processed mRNA transcripts are recognized and transported to the cytoplasm through nuclear pores.

d

Which statement about the lactose operon is incorrect? a. The lacZ is coding for β-galactosidase and lacY is coding for lactose permease are genes called structural genes. b. lacl is a gene sequence coding for the repressor which binds to the operator, inhibiting transcription. c. The promoter sequence recruits RNA polymerase complex and the initiation of transcription. d. lacO is a sequence coding for the operator. e. The CRP-cAMP binding site promotes transcription of lactose operon genes if cAMP is high, which indicates that glucose is low and lactose metabolism is needed for energy production.

d

Which statement about the lactose operon is incorrect? a. The promoter sequence recruits RNA polymerase complex and the initiation of transcription. b. lacl is a gene sequence coding for the repressor which binds to the operator, inhibiting transcription. c. The lacZ is coding for β-galactosidase and lacY is coding for lactose permease are genes called structural genes. d. lacO is a sequence coding for the operator. e. The CRP-cAMP binding site promotes transcription of lactose operon genes if cAMP is high, which indicates that glucose is low and lactose metabolism is needed for energy production.

d

Which statement accurately describes DNA methylation? a. Methyl groups are added to most bases in the promoter region of a specific gene so that RNA polymerase and its associated proteins will bind more efficiently. b. Methyl groups are most often added to guanines adjacent to cytosines bases in or near the promoter sequence, increasing the probability of gene expression. c. Methyl groups are most often added to cytosines adjacent to guanine bases in or near the promoter sequence, increasing the probability of gene expression. d. Methyl groups are most often added to cytosines adjacent to guanine bases in or near the promoter sequence, decreasing the probability of gene expression. e. Methyl groups are most often added to adenine-thymine base pairs, and this increases the probability of gene expression.

d

Active β-galactosidase enzyme is observed only in E. coli growing in the presence of lactose. One hypothesis is that the enzyme is always being produced but is produced in an unstable form that breaks down rapidly in the absence of lactose (hypothesis 1). A second hypothesis is that the enzyme is stable but is produced only in the presence of lactose (hypothesis 2). An experiment was performed to test these hypotheses. A culture of growing cells was exposed to lactose, which was later removed. The amount of β-galactosidase present in the culture during the course of the experiment was measured. The data are shown in the following graph. Which statement is a conclusion that can be obtained from these experimental data? a. The amount of β-galactosidase in the culture decreased rapidly after lactose was removed, in support of hypothesis 2. b. The amount of β-galactosidase in the culture decreased rapidly after lactose was removed, in support of hypothesis 1. c. Synthesis of β-galactosidase is turned on when lactose is added and turned off when lactose is removed, in support of hypothesis 1. d. The amount of β-galactosidase in the culture remained stable after lactose was removed, in support of hypothesis 1. e. Synthesis of β-galactosidase is turned on when lactose is added and turned off when lactose is removed, in support of hypothesis 2.

e

In gene expression in eukaryotes, the primary transcript is transported unchanged directly to the cytoplasm and is ready for translation. - true - false

false

In prokaryotes, when the promoter is bound to the repressor, the operator recruits the RNA polymerase complex and transcription of polycistronic RNA occurs. true. false.

false

Primary RNA transcripts never splice differently so that the same primary transcript generated from a single gene can give rise only to one kind of processed mRNA transcript and thus to one kind of protein. true false

false

The lactose operon is an example of positive regulation by an inducer whose function is modulated by a repressor. true false

false

The miRNA-RISC-mRNA complex enhances the translation efficiency of the mRNA transcript. true false

false

Refer to the drawing of mRNA shown. Click to view full size. Choose the letter that best fits the description. The protein-coding region corresponds to:

region c

A functional RISC targets RNA molecules containing one or more regions that can undergo base pairing with the small regulatory RNA incorporated in the RISC. true false

true

After small regulatory RNAs are transcribed and processed, specialized enzymes cleave the RNAs to double-stranded fragments that are typically around 20-25 nucleotides long. true false

true

Depending on the type of small regulatory RNA, the RNA sequence in the RISC, and the particular type of RISC, the small regulatory RNA may result in chromatin remodeling, degradation of RNA transcripts, or inhibition of mRNA translation. true false

true

Gene regulation in multicellular organisms leads to differential gene expression and specialized cell functions. true false

true

In bacteriophage that can undergo the lytic cycle or lysogeny, an excess of cro protein is associated with the lytic cycle. true false

true

It is likely that over half of human proteins have their synthesis regulated by miRNAs. true false

true

Methylated cytosines are often observed in CpG islands near genes that are repressed. true false

true

Modification of bases in mRNA transcripts can change the mRNA sequence and thus the characteristics of the protein for which it codes. true false

true

Primary RNA transcripts from a gene are sometimes spliced in different ways and can produce multiple different mRNAs. true false

true

The alternative lytic and lysogenic pathways are determined by positive and negative regulatory effects of proteins produced by the virus following infection. true false

true

Transcription in prokaryotes is rapidly turned on or off in response to environmental changes and involves both positive and negative regulators. true false

true

Unlike processing of the primary transcript, RNA editing occurs at the level of mRNA. true false

true

Untranslated regions of the mRNA transcript may interact with motor proteins to enhance transport of the mRNA to a distinct region of the cell; or these regions may interact with proteins that repress the translation of the mRNA. true false

true