Deck 19: Genetic and Epigenetic Regulation

Question 1

A histone code is the:

A)nucleotide sequence of an individual histone protein's gene.
B)pattern of chemical modification of the DNA wrapped around an individual histone.
C)pattern of chemical modification of the histone tails.
D)number of amino acids in an individual histone that are methylated.
E)None of the other answer options is correct.

Answer 1

C

Question 2

Which of the following processes produce different proteins in different cells from the same primary transcript?

A)chromatin remodeling
B)histone modification
C)combinatorial control
D)alternative splicing
E)RNA editing

Answer 2

D, E

Question 3

A researcher notices that women working in the petrochemical industry who are exposed to aromatic hydrocarbons may have a greater incidence of breast cancer than women without such exposure. The researcher undertakes a study of the BRCA1 promoter using the restriction enzymes MspI and HpaII. MspI cleaves double-stranded DNA at 5'-CCGG-3' regardless of whether the CG in the middle has cytosine methylation, whereas HpaII cleaves double-stranded DNA at 5'-CCGG-3' only when the CG in the middle lacks cytosine methylation. For a region of double-stranded DNA in the promoter region of BRCA1, tumor cells from the breasts of exposed women with breast cancer and nontumor cells from breasts from the same women show the illustrated patterns of bands produced by MspI and HpaII: Which of the following statements are supported by this evidence?

A)More sites are methylated in tumor cells than in nontumor cells.
B)Fewer sites are methylated in tumor cells than in nontumor cells.
C)The same sites are methylated in tumor cells as in nontumor cells.
D)No sites are methylated in nontumor cells.
E)The BRCA1 gene may be epigenetically silenced in tumor cells.

Answer 3

A, E

Question 4

Transcription of a gene can be increased or decreased according to the:

A)combination of histone proteins found within the nucleosome.
B)coding sequences in the messenger RNAs for histone proteins.
C)proportion of arginine and lysine amino acids in the histone proteins.
D)combination of amino acid modifications in the histone tails.

Question 5

_____ is defined as the process by which information from a gene is used in the synthesis of a functional gene product.

A)Gene expression
B)Gene regulation
C)Epigenetics
D)Imprinting
E)Chromatin remodeling

Question 6

The methylation state of an individual CpG island:

A)is fixed; such genes are permanently turned off.
B)is fixed, but this has no effect on whether genes are expressed.
C)is random-sometimes the cytosines are methylated and sometimes they're not, but the state is independent of the environment or cell type.
D)can change over time in response to environmental cues, allowing genes to be turned on or off as needed.
E)can change over time in response to environmental cues, but this has no effect on gene expression.

Question 7

Chromatin remodeling refers to the process by which:

A)nucleosomes are repositioned to expose different stretches of DNA to the nuclear environment.
B)DNA strands are "straightened out" to allow access to the proteins that carry out transcription.
C)DNA strands are "unzipped" to allow access to the proteins that carry out transcription.
D)methylation occurs in CpG islands.
E)mutations change DNA structure and therefore chromatin structure.

Question 8

In the hierarchy of levels of gene regulation, in what order do the following levels of regulation take place? (1) post-translational modification
(2) RNA processing
(3) transcription
(4) chromatin remodeling

A)(1)-(2)-(3)-(4)
B)(4)-(3)-(2)-(1)
C)(1)-(3)-(2)-(4)
D)(4)-(1)-(2)-(3)
E)(4)-(2)-(3)-(1)

Question 9

X-inactivation is caused by the accumulation of:

A)proteins produced by the Xist gene; these proteins induce methylation, histone modification, and other changes associated with preventing transcription.
B)coding RNA produced by the Xist gene; this RNA, in addition to coding for Xist proteins, binds to and coats the X chromosome undergoing inactivation and physically prevents it from being transcribed.
C)noncoding RNA produced by the Xist gene, which coats the X chromosome and covalenty crosslinks the DNA strands preventing them from being unwound, "unzipped," and transcribed.
D)noncoding RNA produced by the Xist gene, which coats the X chromosome and induces DNA methylation, histone modification, and other changes associated with preventing transcription.
E)None of the answer choices accurately describes the process of X-inactivation.

Question 10

Which process produces multiple proteins from the same primary transcript in the same cell?

A)chromatin remodeling
B)histone modification
C)combinatorial control
D)alternative splicing
E)RNA editing

Question 11

In humans and other mammals, X-inactivation takes place:

A)early in development, with each new cell inheriting the same inactivated X chromosome as its parent cell.
B)late in development, with each new cell inheriting the same inactivated X chromosome as its parent cell.
C)throughout the lifetime of an organism-with each new cell division, both X chromosomes are activated, and one is then inactivated in each new cell.
D)early in development, with all maternal X chromosomes being inactivated and cells maintaining active copies of only the paternal X chromosome.
E)early in development, with all paternal X chromosomes being inactivated and cells maintaining active copies of only the maternal X chromosome.

Question 12

A CpG island is:

A)a stretch of nucleotides with many C bases adjacent to G bases in a small region near or in the promoter site of a gene.
B)a stretch of nucleotides with many C bases adjacent to G bases found anywhere along a DNA strand.
C)a stretch of nucleotides with many C bases adjacent to G bases found near bacterial operons.

Question 13

The diagram shown here is part of an RNA transcript containing four open reading frames (M, H, K, and L) and three introns (1, 2, 3). The sites labeled d1-d3 are nucleotides immediately before each intron on the 5' side and those labeled a1-a3 are nucleotides immediately after each intron on the 3' side. Splicing out an intron involves cleaving the DNA at the d and a sites at either end of the intron. A missense mutation takes place in open reading frame K. In which possible alternative splice forms of the transcript would the missense mutation not affect the polypeptide product?

A)d1-a1 + d2-a2 + d3-a3
B)d1-a2 + d3-a3
C)d1-a1 + d2-a3
D)d1-a3
E)None of the answer options is correct.

Question 14

The diagram shown here is part of an RNA transcript containing four open reading frames (M, H, K, and L) and three introns (1, 2, 3). The sites labeled d1-d3 are nucleotides immediately before each intron on the 5' side and those labeled a1-a3 are nucleotides immediately after each intron on the 3' side. Splicing out an intron involves a spliceosome facilitating the cleavage of the DNA at the d and a sites at either end of the intron. A missense mutation takes place in open reading frame H. In which possible alternative splice forms of the transcript would the missense mutation not affect the polypeptide product?

A)d1-a1 + d2-a2 + d3-a3
B)d1-a2 + d3-a3
C)d1-a1 + d2-a3
D)d1-a3
E)None of the answer options is correct.

Question 15

Modifications of histone tails can:

A)affect chromatin structure.
B)activate transcription of some genes.
C)repress transcription of some genes.
D)affect expression of some genes in response to the environment.
E)All of these choices are correct.

Question 16

Sex-specific silencing of gene expression is known as:

A)X-inactivation.
B)methylation.
C)chromatin remodeling.
D)imprinting.
E)None of the answer options is correct.

Question 17

In mammals, dosage compensation refers to a mechanism in which:

A)the level of expression for a given gene is directly related to the number of copies of the gene.
B)genes in the Y chromosome must be expressed at higher levels than would otherwise be the case because they are not homologous with genes on the X chromosome.
C)genes in the X chromosome must be expressed at lower levels than would otherwise be the case because they are not homologous with genes on the Y chromosome.
D)X chromosome genes are regulated differently in males and females because members of one sex have two X chromosomes, whereas members of the other have only one.
E)None of the answer options is correct.

Question 18

In general, when cytosine bases in CpG islands are methylated:

A)transcription is active and rapid.
B)transcription is active, but slow.
C)transcription is repressed.
D)translation is active and rapid.
E)translation is repressed.

Question 19

The diagram shown here is part of an RNA transcript containing four open reading frames (M, H, K, and L) and three introns (1, 2, 3). The sites labeled d1-d3 are nucleotides immediately before each intron on the 5' side and those labeled a1-a3 are nucleotides immediately after each intron on the 3' side. Splicing out an intron involves a spliceosome facilitating the cleavage of the DNA at the d and a sites at either end of the intron. How many processed transcripts are possible in which two d sites and two a sites are cleaved?

A)one
B)two
C)three
D)four
E)five

Question 20

Two related but distinct neurological disorders are Prader-Willi syndrome (PWS) and Angelman syndrome (AS). Children with PWS are obese, have weak muscle tone, and delayed development. Children with AS have severe speech impairment, developmental delay, intellectual disability, and problems with movement and balance. However, both disorders are due to the deletion of the same part of chromosome 15. When the deletion is in the copy of chromosome 15 that came from the father, the child has PWS, but when the deletion is in the copy of chromosome 15 that came from the mother, the child has AS. What hypothesis can explain these observations?

A)unequal crossing over
B)parental imprinting
C)dosage compensation
D)alternative splicing
E)combinatorial control

Question 21

Methylation is a mechanism often used by cells to prevent the expression of:

A)genes in transposable elements.
B)genes from viruses that have been integrated into the genome.
C)harmful (mutant)genes such as those responsible for cystic fibrosis.

Question 22

The diagram shown here is part of an RNA transcript containing four open reading frames (M, H, K, and L) and three introns (1, 2, 3). Splicing out an intron involves a spliceosome facilitating the cleavage of the DNA at nucleotides on either side of the intron. How many processed transcripts are possible if all three 5' nucleotides (immediately before each intron) and all three 3' nucleotides (immediately after each intron) are cleaved?

A)1
B)2
C)3
D)4
E)5

Question 23

In the type of RNA editing in which C is converted to U, which codons could be converted to a stop codon?

A)ACG
B)CAA
C)ACC
D)CAG
E)CGA

Question 24

The human body contains approximately 200 major cell types. They look and function differently from one another because each:

A)has a slightly different genome.
B)expresses a different set of genes.
C)expresses the same set of genes, but in different orders at different times.
D)has a slightly different genome and each expresses a different set of genes.

Question 25

Chromatin may be remodeled by:

A)chemical modification of the nucleotide bases of the DNA.
B)mutations affecting the structure of the chromosome's nonhistone proteins.
C)chemical modification of the chromosome's histone proteins.

Question 26

RNA splicing provides an opportunity for regulating gene expression because:

A)the same exons may be spliced together in different sequences to produce different proteins from the same primary transcript.
B)the same introns may be spliced together in different sequences to produce different proteins from the same primary transcript.
C)a spliceosome in one cell can "see" as an intron what another spliceosome in another cell "sees" as an exon, allowing different proteins to be produced from the same primary transcript.
D)methylation of spliceosomes controls how rapidly primary transcripts are processed and sent to the cytoplasm.
E)methylation of the poly(A)tail controls how rapidly the primary transcript can be broken up and spliced back together again.

Question 27

Epigenetic modifications can:

A)be inherited.
B)be reversed.
C)alter gene expression.
D)change the sequence of the DNA.

Question 28

Combinatorial control refers to a regulatory mechanism in which:

A)transcription is initiated by a combination of sites in the promoter.
B)transcription is terminated by a combination of sites in the terminator.
C)each alternatively spliced transcript has a different combination of exons.
D)transcription requires a specific combination of transcription factors.
E)None of the answer options is correct.

Question 29

X-inactivation is an example of:

A)post-transcriptional modification.
B)epigenetic gene regulation.
C)dosage compensation.
D)positive regulation by CRP-cAMP.
E)miRNA-induced silencing.

Question 30

Enhancer sequences are bound by:

A)RNA splicing complexes.
B)RNA editing complexes.
C)histone-modifying complexes.
D)cytosine methylation enzymes.
E)transcription factors.

Question 31

Gene regulation can occur through:

A)DNA modification.
B)histone modification.
C)RNA modification.
D)All of these choices are correct.

Question 32

The diagram shown here is part of an RNA transcript containing four open reading frames (M, H, K, and L) and three introns (1, 2, 3). How many cuts would a spliceosome have to make in order to result in a transcript containing only open reading frames M, K, and L?

A)0
B)1
C)2
D)3
E)4

Question 33

Epigenetic mechanisms can include:

A)chromatin remodeling.
B)histone modification.
C)cytosine methylation.
D)X-inactivation.
E)combinatorial control.

Question 34

Many genes have multiple enhancer sequences. The multiple enhancer sequences allow multiple:

A)options for alternative splicing of the RNA transcript.
B)options for RNA editing of the RNA transcript.
C)transcription factors to control gene expression.
D)proteins to be made from the same protein-coding gene.
E)None of the answer options is correct.

Question 35

Humans with hypohidrotic ectodermal dysplasia have defects in the formation and function of their sweat glands. Males with the condition have reduced ability to sweat over their entire body. Females with the condition lose the ability to sweat only in patches of skin. Where must the gene that encodes this trait be located?

A)in the Y chromosome
B)in the X chromosome
C)in an autosome

Question 36

Alternative splicing may be considered a mechanism of gene regulation because it:

A)results in DNA rearrangements.
B)enhances RNA editing.
C)results in different protein products.
D)is mutagenic.

Question 37

Lifestyle choices that can affect levels of gene expression include:

A)diet.
B)exercise.
C)drug abuse.
D)meditation.
E)inherited mutation.

Question 38

One type of RNA editing converts Cs to Us. In how many codons in the genetic code would such a change NOT affect what amino acid is translated?

A)20
B)22
C)24
D)25
E)27

Question 39

A single gene can produce different proteins.

Question 40

A woman is heterozygous for a recessive allele that causes X-linked hemophilia. This recessive allele has a mutation that makes a gene for a blood-clotting factor nonfunctional. Considering the implications of X-inactivation, the level of clotting factor in her blood is likely to be approximately _____ that of a homozygous nonmutant woman.

A)1)0
B)3/4
C)1/2
D)1/4
E)None of the answer options is correct.

Question 41

Histone modification:

A)is fixed; once a histone is modified, it stays that way and the genes with which it is associated are turned on or off permanently.
B)is fixed, but this has no effect on whether genes are expressed.
C)is random-sometimes the lysines are modified and sometimes they're not, but the state is independent of the environment or cell type.
D)can change over time in response to environmental cues, allowing genes to be turned on or off as needed.
E)can change over time in response to environmental cues, but this has no effect on gene expression.

Question 42

In humans and other mammals, genes in the inactivated X chromosome:

A)are not transcribed at all.
B)may be transcribed at a low level.
C)are expressed at exactly half the level of an autosomal gene.
D)are transcribed but not translated.

Question 43

In humans and other mammals, dosage compensation is achieved by:

A)males transcribing twice the normal amount of copies of X-chromosome genes.
B)females decreasing transcription of both X chromosomes by half.
C)females eliminating one X chromosome in each cell.
D)females inactivating the paternal X chromosome in each cell.
E)females randomly inactivating one X chromosome in each cell.

Question 44

Epigenetic mechanisms of gene regulation include:

A)changes to DNA sequences.
B)the way in which DNA is packaged within chromosomes.
C)the way in which chromosomes are organized into genomes.
D)repression by binding of repressor proteins.
E)chemical modifications to DNA.

Question 45

Insulin is needed to regulate sugar levels in the blood. While every cell in the body contains genes for the production of insulin, it is only produced by a specialized subset of cells in the pancreas. Therefore:

A)every cell must regulate its own sugar production.
B)the genes for insulin production must be mutated except in the specialized cells of the pancreas.
C)there must be mechanisms of gene regulation that promote insulin expression in the specialized pancreatic cells and prevent insulin expression in all other cells.
D)only the specialized cells of the pancreas have functional genes for insulin production.
E)insulin production is not regulated because the genes for it are present in every cell.

Question 46

The process by which a single primary RNA transcript is used to make multiple proteins is called:

A)combinatorial control.
B)alternative splicing.
C)regulatory splicing.
D)translational control.
E)polymerization control.

Question 47

In RNA editing:

A)spliceosomes 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)enzymes change the base sequence of the primary transcript and therefore the protein for which it codes.
D)microRNAs in different cells create different primary RNA transcripts from the same DNA sequence.
E)a combination of spliceosomes and enzymes creates different primary RNA transcripts from the same DNA sequence.

Question 48

Gene regulation by means of epigenetic mechanisms is useful to the organism because it:

A)does not require new mutations.
B)can quickly be reversed.
C)can respond rapidly to environmental change.
D)can differ between the sexes.
E)All of these choices are correct.

Question 49

Epigenetic mechanisms of gene regulation _____ inherited by daughter cells and are _____.

A)can be; permanent
B)can be; often reversible and responsive to environmental change
C)can be; random with respect to the environment
D)are not; reversible and responsive to environmental change
E)are not; permanent

Question 50

Regulatory transcription factors:

A)bind to DNA sequences in or near gene enhancers.
B)recruit the components of the general transcriptional factors.
C)recruit the components of the RNA polymerase complex.

Question 51

In domestic cats, the coat-color pattern known as calico is an example of:

A)gene regulation at the level of the chromosome.
B)dosage compensation.
C)epigenetic regulation.
D)X-inactivation.
E)All of these choices are correct.

Question 52

A woman is heterozygous for X-linked color blindness. Considering the implications of X-inactivation, her phenotype is:

A)likely to be color blind.
B)likely to be color blind in one eye.
C)likely to be normal color vision.
D)unpredictable.

Question 53

Although lifestyle choices cannot, in general, change our genomes, they can:

A)change the physiological states of our cells, which in turn affects post-translational gene regulation.
B)increase the rate at which some genes are transcribed.
C)decrease the rate at which some genes are transcribed.
D)change the genetic code for translation.
E)change the metabolic pathways of glycolysis.

Question 54

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

Question 55

Gene regulation can occur at which of the following steps in the path from DNA to protein?

A)during transcription from a chromosome
B)during translation from DNA to RNA
C)after protein synthesis
D)during transcription from a chromosome and during translation from DNA to RNA
E)during transcription from a chromosome, during translation from DNA to RNA, and after protein synthesis

Question 56

In the type of RNA editing in which C is converted to U, which of the codons listed below could be converted to AUG?

A)AGC
B)GCA
C)AUG
D)ACG

Question 57

Which of the following questions is about gene regulation?

A)Why do all eukaryotes share a common genetic code?
B)Where are genes for hemoglobin expressed?
C)How much insulin is produced after a meal?

Question 58

A cell could potentially regulate transcription by adjusting the number and kinds of:

A)regulatory transcription factors present.
B)general transcription factors present.
C)components of the RNA polymerase complex present.

Question 59

Methylation, acetylation, and other histone modifications are important because they are associated with:

A)chromatin remodeling and affect gene transcription.
B)CpG island methylation and affect gene transcription.
C)cancer genes and their regulation.
D)the environmental and developmental cues that determine whether viral genes and genes in transposable elements are turned off or on.

Question 60

Which one of the following statements about gene regulation is INCORRECT?

A)Gene regulation occurs at the level of the chromosome.
B)Gene regulation occurs at the level of transcription.
C)Gene regulation occurs only in prokaryotes.
D)Gene regulation occurs at the translational level.
E)Gene regulation occurs at the post-translational level.

Question 61

Which one of the following statements MOST accurately describes methylation?

A)Methyl groups are most often added to cytosines adjacent to guanine bases in or near the promoter sequence, increasing the probability of gene expression.
B)Methyl groups are most often added to cytosines adjacent to guanine bases in or near the promoter sequence, decreasing the probability of gene expression.
C)Methyl groups are most often added to adenine-thymine base pairs because they are held by only two hydrogen bonds, and this increases the probability of gene expression.
D)Methyl groups are most often added to guanine-cytosine base pairs because they are held by three hydrogen bonds, and this decreases the probability of gene expression.
E)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.

Question 62

The type of gene regulation in which transcription of a gene depends on the presence of a particular combination of enhancers and other regulatory transcription factors is known as _____ control.

A)histone
B)epigenetic
C)polynomial
D)combinatorial
E)recombinational

Question 63

Nucleosomes occupy fixed positions along the DNA that remain the same over time and in each cell.

Question 64

Which one of the following describes an event that takes place during gene regulation at the level of the chromosome?

A)Chromatin becomes condensed in order for transcription to begin.
B)Chromatin coils so it can become more accessible to the proteins that carry out transcription.
C)RNA polymerase and associated proteins bind to nucleosomes.
D)Chromatin is remodeled and nucleosomes are repositioned so that specific regions of the DNA are made available for transcription.
E)Cytosine bases in the sequence near the promoter of a gene become methylated in order to stimulate transcription.

Question 65

Amino acid sequences that are rich in lysine and protrude from the histone proteins in the nucleosome are called "tails."

Question 66

In gene expression in eukaryotes, the primary transcript is transported directly to the cytoplasm and prepared for translation.

Question 67

Modifications of bases, changes to histones, and alterations in chromatin structure that regulate gene expression are said to be:

A)nonheritable.
B)post-translational.
C)supragenetic.
D)epigenetic.
E)synchrogenetic.

Question 68

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

Question 69

The first level of gene regulation occurs along the chromosome, through chemical modifications of the DNA or histones.

Question 70

Which one of the following statements about the methylation state of CpG islands is INCORRECT?

A)Cells can heavily methylate CpG islands of viral DNA sequences in order to restrict their expression.
B)Cells can heavily methylate CpG islands of genes in transposable elements in order to restrict their expression.
C)The methylation state of CpG islands provides a way to turn genes on or off.
D)The methylation state of CpG islands is static and will not change over time.
E)The methylation state of CpG islands can change in response to the environment.

Question 71

Heavy methylation of CpG islands is usually associated with repression of transcription.

Question 72

Transcriptional regulation in eukaryotic cells requires the coordinated action of many proteins that interact with one another and with DNA sequences near the gene.

Question 73

All CpG sites located near the promoter region of protein coding genes are methylated.

Question 74

Histone modification occurs only during early development.

Question 75

Patterns of histone methylation and acetylation that affect chromatin structure and gene transcription constitute a _____ code.

A)genetic
B)DNA
C)histone
D)protein

Question 76

RNA splicing joins together the coding regions of messenger RNA in their original linear order after the removal of introns.

Question 77

In female humans and other mammals, dosage compensation is achieved by the inactivation of one of the two X chromosomes in each cell. Which one of the following does NOT occur in the X-inactivation mechanism of female mammals?

A)X-inactivation begins with a small region of the X chromosome that contains a gene for an X- inactivation specific transcript (Xist).
B)Xist is expressed in low levels except when an X chromosome is about to be inactivated.
C)When an X chromosome is about to be inactivated, Xist RNA transcripts increase markedly and undergo splicing, but do not encode a protein.
D)Xist RNA is attracted to and associates with a protein called the X-chromosome inactivation center (XIC), which becomes entirely coated with Xist.
E)Xist RNA recruits factors that promote DNA methylation, histone modification, and other changes associated with transcriptional silencing.

Question 78

Which of the following statements about transcriptional regulation is INCORRECT?

A)Regulatory transcription factors are proteins that bind to enhancer DNA sequences and then recruit one or more general transcription factors.
B)A typical gene contains only one enhancer sequence.
C)General transcription factors are required to initiate the process of transcription.
D)General transcription factors bind to the TATA box in the promoter region of a gene.
E)RNA polymerase components are recruited to the promoter region by the general transcription factors bound to the TATA box.

Question 79

The complex of DNA, RNA, and associated proteins that gives shape to the chromosome is called:

A)chromatin.
B)histones.
C)an operon.
D)a scaffold.

Question 80

What happens when the Xist gene from an X chromosome is inserted into an autosome?

A)Gene activity in the autosome remains normal.
B)The autosome with Xist is inactivated like an X chromosome.
C)The autosome with Xist is inactivated in half the cells, and the homologous autosome is inactivated in the other half.
D)Both the autosome and its homologous chromosome are inactivated.