Deck 19: Control of Gene Expression in Eukaryotes

Question 1

If a cell were unable to produce histone proteins, which of the following would be a likely effect?

A) There would be an increase in the amount of "satellite" DNA produced during centrifugation.
B) The cell's DNA couldn't be packed into its nucleus.
C) Spindle fibers would not form during prophase.
D) Amplification of other genes would compensate for the lack of histones.

Answer 1

B

Question 2

Which of the following statements describes a eukaryotic chromosome?

A) a single strand of DNA
B) a series of nucleosomes wrapped around two DNA molecules
C) a chromosome with different numbers of genes in different cell types of an organism
D) a single linear molecule of double-stranded DNA plus proteins

Answer 2

D

Question 3

Which of the following is most critical for the association between histones and DNA?

A) Histones are small proteins.
B) Histones are highly conserved (that is, histones are very similar in every eukaryote).
C) Histones are synthesized in the cytoplasm.
D) There are at least five different histone proteins in every eukaryote.
E) Histones are positively charged.

Answer 3

E

Question 4

Several of the different globin genes are expressed in humans but at different times in development. What mechanism could allow for this?

A) exon shuffling
B) intron activation
C) pseudogene activation
D) differential translation of mRNAs
E) differential gene regulation over time

Question 5

Which of the following statements about the DNA in one of your brain cells is TRUE?

A) Most of the DNA codes for protein.
B) All of the genes of the genome are likely to be transcribed.
C) Each gene lies immediately adjacent to an enhancer.
D) Many related genes are transcribed from a single promoter.
E) It is the same as the DNA in one of your heart cells.

Question 6

Which of the following allows more than one type of protein to be produced from one gene?

A) alternative forms of chromatin remodeling
B) alternative forms of RNA splicing
C) alternative forms of nucleosomes
D) control of the frequency of translation initiation

Question 7

Why do histones bind tightly to DNA?

A) Histones are positively charged, and DNA is negatively charged.
B) Histones are negatively charged, and DNA is positively charged.
C) Both histones and DNA are strongly hydrophobic.
D) Histones are covalently linked to the DNA.
E) Histones are highly hydrophobic, and DNA is hydrophilic.

Question 8

At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. Many people were surprised that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for much of the DNA that is NOT coding for proteins?

A) most of the DNA serving as origins of DNA replication
B) DNA that consists of histone coding sequences
C) DNA that is translated directly without being transcribed
D) non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function
E) non-protein-coding DNA that serves as binding sites for reverse transcriptase

Question 9

The predominant mechanism driving cellular differentiation is the difference in gene ________.

A) expression
B) sequences
C) order
D) replication

Question 10

If you were to observe the activity of methylated DNA, you would expect it to ________.

A) be replicating nearly continuously
B) be unwinding in preparation for protein synthesis
C) have turned off or slowed down the process of transcription
D) be very actively transcribed and translated
E) induce protein synthesis by not allowing repressors to bind to it

Question 11

Two potential devices that eukaryotic cells use to regulate transcription are ________.

A) DNA methylation and histone amplification
B) DNA amplification and histone methylation
C) DNA acetylation and methylation
D) DNA methylation and histone modification
E) histone amplification and DNA acetylation

Question 12

Cell differentiation always involves ________.

A) the production of tissue-specific proteins, such as muscle actin
B) the movement of cells
C) the transcription of the myoD gene
D) the selective loss of certain genes from the genome
E) the cell's sensitivity to environmental cues, such as light or heat

Question 13

Use this information to answer the question(s) below.
In one set of experiments she succeeded in increasing acetlylation of histone tails. Which of the following results would she most likely see?

A) increased chromatin condensation
B) decreased chromatin condensation
C) activation of histone tails for enzymatic function
D) decreased binding of transcription factors
E) inactivation of the selected genes

Question 14

Cloning of plants from cuttings demonstrates that ________.

A) an individual plant cell cannot de-differentiate and then re-differentiate
B) differentiated plant cells may contain embryonic mRNAs
C) plants lose genetic information in the differentiation process
D) mature plant cells retain the full genetic information needed to carry out the developmental processes to produce a new individual plant

Question 15

Which of the following statements is TRUE of histones?

A) Each nucleosome consists of two molecules of histone H1.
B) Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.
C) The carboxyl end of each histone extends outward from the nucleosome and is called a "histone tail."
D) Histones are found in mammals but not in other animals or in plants or fungi.

Question 16

Mammals have a family between 500 and 1000 genes that encode receptor proteins on the surface of odor-receptor neurons. If all mammals have these genes, why do some mammals have a better sense of smell than others do?

A) Some of the genes actively transcribing receptor proteins in some species are completely absent in other species.
B) Some of the genes may have been mutated and rendered inactive in some species but not in others.
C) Some species, particularly humans, rely much less on odor detection for survival; thus, the genes have mutated to encode proteins that aid in other senses, such as sight.
D) Some species of mammals have a larger set of "basic odors" than other species.

Question 17

Muscle cells differ from nerve cells mainly because they ________.

A) express different genes
B) contain different genes
C) use different genetic codes
D) have unique ribosomes
E) have different chromosomes

Question 18

DNA methylation and histone acetylation are examples of ________.

A) genetic mutation
B) chromosomal rearrangements
C) karyotypes
D) epigenetic phenomena
E) translocation

Question 19

Which method is utilized by eukaryotes to control their gene expression that is NOT used in bacteria?

A) control of chromatin remodeling
B) control of RNA splicing
C) transcriptional control
D) control of both RNA splicing and chromatin remodeling
E) control of chromatin remodeling, RNA splicing, and transcription

Question 20

In a nucleosome, the DNA is wrapped around ________.

A) polymerase molecules
B) ribosomes
C) histones
D) a thymine dimer
E) satellite DNA

Question 21

The primary difference between enhancers and promoter-proximal elements is that enhancers ________.

A) are transcription factors; promoter-proximal elements are DNA sequences
B) enhance transcription; promoter-proximal elements inhibit transcription
C) are part of the promoter; promoter-proximal elements are regulatory sequences distinct from the promoter
D) are at considerable distances from the promoter; promoter-proximal elements are close to the promoter
E) are DNA sequences; promoter-proximal elements are proteins

Question 22

In eukaryotes, the normal or default state is that genes are turned ________.

A) off through their association in nucleosomes
B) off through their association with exons
C) on through their association with exons
D) on through their association in nucleosomes

Question 23

The reason for differences in the sets of proteins expressed in a nerve and a pancreatic cell of the same individual is that nerve and pancreatic cells contain different ________.

A) genes
B) regulatory sequences
C) sets of regulatory proteins
D) promoters
E) promoter-proximal elements

Question 24

Imagine that you have isolated a yeast mutant that contains a constitutively (constantly) active histone deacetylase. What phenotype do you predict for this mutant?

A) The mutant will grow rapidly.
B) The mutant will require galactose for growth.
C) The mutant will show low levels of gene expression.
D) The mutant will show high levels of gene expression.

Question 25

The B-I mutation in anthocyanin (red pigments) produces pigmented corn plants, whereas the B′ mutation in the same gene usually produces nearly unpigmented corn plants when homozygous (B´/B´). When homozygous B-I and B′ plants are intercrossed, the F1 plants are essentially unpigmented, like the B′ homozygotes. If this outcome were due simply to the dominance of B′ to B-I, then a self-cross of the F1 plants (B´/B-I) should generate B-I-colored homozygotes as approximately 1/4 (B-I/B-I) of the F2 progeny. Instead, no F2 are pigmented. Intercrosses of the F2 and of further generations do not restore the pigmented phenotype. What is the term for this type of inheritance?

A) Mendelian inheritance
B) organelle genome inheritance
C) allelic inheritance
D) epigenetic inheritance

Question 26

An example of a basal transcription factor is ________.

A) RNA polymerase
B) the TATA-binding protein
C) an enhancer-binding transcription factor
D) a silencer-binding transcription factor
E) a promoter-proximal-binding transcription factor

Question 27

Activator proteins in eukaryotes usually have a domain that binds to DNA and other activation domains that often bind to ________.

A) DNA polymerases
B) ATP
C) protein-based hormones
D) other regulatory proteins
E) tRNA

Question 28

Imagine that you've isolated a yeast mutant that contains histones resistant to acetylation. What phenotype do you predict for this mutant?

A) The mutant will grow rapidly.
B) The mutant will require galactose for growth.
C) The mutant will show low levels of gene expression.
D) The mutant will show high levels of gene expression.

Question 29

If the DNA sequence was substantially altered from one of the following, which would prevent the binding of the TATA-binding protein (TBP)?

A) RNA polymerase
B) the point where transcription begins
C) the promoter
D) promoter-proximal elements
E) histone acetyl transferases (HATS)

Question 30

Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells?

A) Environmental signals enter the cell and bind directly to promoters.
B) The genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time.
C) The genes are organized into a large operon, allowing them to be coordinately controlled as a single unit.
D) A single repressor is able to turn off several related genes.

Question 31

If cells of an individual contain the same set of genes, how do these cells become different from each other during development?

A) Different cell type-specific regulatory elements in DNA are created during development.
B) Different cell type-specific regulatory elements in DNA are selectively lost during development.
C) Differences in extracellular signals received by each cell lead to differences in the types of regulatory proteins present in each cell.
D) Differences develop in promoter sequences that lead to different signals being produced by each type of cell.

Question 32

Twenty-five years ago, when Oshima and colleagues discovered that a mutation in the GAL4 gene led to the inability to synthesize all five enzymes required for galactose catabolism (breakdown), they couldn't be blamed for wanting to apply a bacterial model to explain this finding. What they expected, but did not find, was ________.

A) that all five genes constitute an operon
B) five widely separated genes, each containing a GAL4-binding site in its regulatory region
C) that chromatin decondensation played an important role in regulating the genes of galactose catabolism
D) that transcription is important in regulating the genes of galactose catabolism

Question 33

The functioning of enhancers is an example of ________.

A) transcriptional control of gene expression
B) a post-transcriptional mechanism to regulate mRNA
C) the stimulation of translation by initiation factors
D) post-translational control that activates certain proteins
E) a eukaryotic equivalent of prokaryotic promoter functioning

Question 34

Of the following, which is the most current description of a gene?

A) a unit of heredity that causes formation of a phenotypic characteristic
B) a DNA subunit that codes for a single complete protein
C) a DNA sequence that is expressed to form a functional product: either RNA or polypeptide
D) a DNA-RNA sequence combination that results in an enzymatic product
E) a discrete unit of hereditary information that consists of a sequence of amino acids

Question 35

In eukaryotes, general transcription factors ________ .

A) are required for the expression of specific protein-encoding genes
B) bind to other proteins or to the TATA box
C) inhibit RNA polymerase binding to the promoter and begin transcribing
D) usually lead to a high level of transcription even without additional specific transcription factors
E) bind to sequences just after the start site of transcription

Question 36

Imagine that you are studying the control of β-globin gene expression in immature red blood cells. (Mature red blood cells contain β-globin protein but lack a nucleus and, therefore, the β-globin gene.) If you deleted a sequence of DNA outside the protein-coding region of the β-globin gene and found that this increased the rate of transcription, the deleted sequence likely functions as ________.

A) a promoter
B) a promoter-proximal element
C) an enhancer
D) a silencer
E) any of the listed functions

Question 37

Regulatory transcription factors ________.

A) influence the binding of sigma factor to DNA
B) influence the assembly of the basal transcription complex
C) influence the degree of unwinding of DNA at the promoter
D) open the two strands of DNA so that RNA polymerase can begin transcription

Question 38

How do chromatin-remodeling complexes recognize the genes they should act on? Chromatin-remodeling complexes ________.

A) are activated by specific extracellular signals that direct them to particular genes
B) recognize specific promoters when they are phosphorylated, methylated, or acetylated
C) recognize specific transcription factors bound to regulatory sequences of DNA
D) bind to the basal transcription complex

Question 39

Use this information to answer the question(s) below.
One of her colleagues suggested she try increased methylation of C nucleotides in the DNA of promoters of a mammalian system. Which of the following results would she most likely see?

A) decreased chromatin condensation
B) activation of histone tails for enzymatic function
C) higher levels of transcription of certain genes
D) inactivation of the selected genes

Question 40

Histone acetyl transferases exert their effect on gene activity by ________.

A) neutralizing positive charges on the lysines of histones
B) introducing negative charges on the glutamic acids of histones
C) modifying the DNA sequence of the promoter
D) increasing the affinity of transcriptional activators for DNA
E) increasing the affinity of transcriptional inhibitors for DNA

Question 41

The product of the p53 gene ________.

A) inhibits the cell cycle
B) slows down the rate of DNA replication by interfering with the binding of DNA polymerase
C) causes cells to reduce expression of genes involved in DNA repair
D) allows cells to pass on mutations due to DNA damage

Question 42

Which of the following is most likely to have a small protein called ubiquitin attached to it?

A) a cyclin protein, which usually acts in G1, in a cell that is in G2
B) a cell surface protein that requires transport from the ER
C) an mRNA leaving the nucleus to be translated
D) a regulatory protein that requires sugar residues to function properly
E) an mRNA produced by an egg cell that will be retained until after fertilization

Question 43

Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells?

A) Proto-oncogenes first arose from viral infections.
B) Proto-oncogenes normally help regulate cell division.
C) Proto-oncogenes are genetic "junk."
D) Proto-oncogenes are mutant versions of normal genes.
E) Cells produce proto-oncogenes as they age.

Question 44

In colorectal cancer, several genes must be mutated for a cell to develop into a cancer cell. Which of the following kinds of genes would you expect to be mutated?

A) genes coding for enzymes that act in the colon
B) genes involved in control of the cell cycle
C) genes that are especially susceptible to mutation
D) genes of the bacteria, which are abundant in the colon

Question 45

Poliovirus is an RNA virus of the picornavirus group, which uses its RNA as mRNA. At its 5' end, the RNA genome has a viral protein (VPg) instead of a 5' cap. This is followed by a nontranslated leader sequence and then a single long protein-coding region (~7000 nucleotides), followed by a poly-A tail. Observations were made that used radioactive amino acid analogues. Short-period use of the radioactive amino acids result in labeling of only very long proteins, while longer periods of labeling result in several different short polypeptides. What conclusion is most consistent with the results of the radioactive labeling experiment?

A) Host cell ribosomes only translate the viral code into short polypeptides.
B) The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones.
C) The RNA is translated into short polypeptides, which are subsequently assembled into large ones.
D) The large radioactive polypeptides are coded by the host, whereas the short ones are coded for by the virus.

Question 46

Proto-oncogenes ________.

A) normally suppress tumor growth
B) were initially introduced into eukaryotic cells by retroviruses
C) are produced by somatic mutations induced by carcinogenic substances
D) stimulate normal cell growth and division
E) are underexpressed in cancer cells

Question 47

Which of the following types of mutation would convert a proto-oncogene into an oncogene?

A) a mutation that blocks transcription of the proto-oncogene
B) a mutation that creates an unstable proto-oncogene mRNA
C) a mutation that greatly increases the amount of the proto-oncogene protein
D) a deletion of most of the proto-oncogene coding sequence

Question 48

Which of the following is TRUE?

A) Mutations that inactivate tumor suppressor genes are important in cancer.
B) Cancer is a single disease with one underlying molecular cause.
C) Uncontrolled cell growth alone is sufficient for the development of cancers.
D) Cancer is a single disease resulting from a common set of mutations.

Question 49

The normal function of a tumor suppressor gene is to ________.

A) suppress the growth of tumors already present in all multicellular eukaryotes
B) prevent progression of the cell cycle unless conditions are right for moving forward
C) prevent meiosis
D) prevent mutations in p53

Question 50

Tumor-suppressor genes ________.

A) are frequently overexpressed in cancerous cells
B) are cancer-causing genes introduced into cells by viruses
C) encode proteins that help prevent uncontrolled cell growth
D) often encode proteins that stimulate the cell cycle

Question 51

Gene expression can be altered more easily at the level of post-transcriptional processing in eukaryotes than in prokaryotes because ________.

A) eukaryotic mRNAs get 5' caps and 3' tails
B) prokaryotic genes are expressed as mRNA, which is more stable in the cell
C) eukaryotic exons may be spliced in alternative patterns
D) prokaryotes use ribosomes of different structure and size

Question 52

Since Watson and Crick described DNA in 1953, which of the following might best explain why the function of small RNAs (miRNAs) is still not well understood?

A) As RNAs have evolved since that time, they have taken on new functions.
B) Watson and Crick described DNA but did not predict any function for RNA.
C) The functions of small RNAs could not be approached until the entire human genome was sequenced.
D) Ethical considerations prevented scientists from exploring this material until recently.
E) Recent advances in technology and our understanding of how DNA is expressed have made this possible.

Question 53

The protein p53 activates genes that ________.

A) increase mutation rate
B) lead to higher production of growth factors for the cell
C) increase the rate of endocytosis
D) arrest the cell cycle

Question 54

Which of the following is an example of post-transcriptional control of gene expression?

A) the addition of methyl groups to cytosine bases of DNA
B) the binding of transcription factors to a promoter
C) the removal of introns and alternative splicing of exons
D) gene amplification contributing to cancer
E) the folding of DNA to form heterochromatin

Question 55

Alternative RNA splicing ________.

A) is a mechanism for increasing the rate of transcription
B) can allow the production of proteins of different sizes and functions from a single mRNA
C) can allow the production of similar proteins from different genes
D) increases the rate of transcription
E) is due to the presence or absence of particular snRNPs

Question 56

The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called ________.

A) RNA interference
B) RNA obstruction
C) RNA blocking
D) RNA targeting
E) RNA disposal