Chapter 6—Changes in DNA: Mutations and Epigenetics
MULTIPLE CHOICE
1. The complete set of genetic information of a human or other organism is called its
a.
genome.
b.
mutation.
c.
chromosome.
d.
phenotype.
e.
genotype.
2. Mutations are only
a.
changes in the nucleotide sequence of DNA.
b.
changes in the amino acid sequence of proteins.
c.
changes in the nucleotide sequence of RNA.
d.
caused by mistakes in DNA replication.
e.
caused by environmental agents.
3. Which of the following statements about mutations is true?
a.
Mutations in body cells can be passed on to future generations.
b.
The only changes due to mutation are in the amino acid sequence of proteins.
c.
Mutations in body cells are not known to cause any phenotypic changes.
d.
All mutations are single-nucleotide substitutions.
e.
Mutations in germ cells can be passed on to future generations.
4. Exposure to radiation
a.
is easily avoidable.
b.
can cause the formation of free radicals.
c.
is entirely from exposure to natural background radiation.
d.
repairs mistakes made during DNA replication.
e.
for the average American is mainly due to dental x-rays.
5. For the average American, _____ of radiation dose is due to background radiation.
a.
19%
b.
50%
c.
70%
d.
81%
e.
99%
6. Researchers have found that when radiation doses are below _____, the major risk is an increase in the
risk of cancer.
a.
100,000 rem
b.
360 mrem
c.
1 rem
d.
5000 rem
e.
5000 mrem
7. Environmental mutagens include certain molecules found in
a.
cigarette smoke.
b.
vehicle exhaust.
c.
some plants.
d.
some processed foods.
e.
all of these.
8. Base analogs
a.
often cause frameshift mutations.
b.
lead to single-nucleotide substitution mutations.
c.
resemble the sugars found in DNA nucleotides.
d.
cause breakage of DNA strands.
e.
resemble the phosphate groups found in DNA nucleotides.
9. Chemicals found in some pesticides
a.
resemble the bases found in DNA.
b.
can lead to frameshift mutations.
c.
change the structure of DNA bases.
d.
cause single-nucleotide substitution mutations.
e.
cause mutations by binding to the DNA polymerase.
10. Chemicals present in some pesticides
a.
resemble the phosphate groups found in DNA.
b.
cause base insertion mutations.
c.
change the structure of DNA bases.
d.
cause single-nucleotide substitution mutations.
e.
cause mutations by binding to the DNA polymerase.
11. The nitrates found in certain food preservatives can cause mutations by
a.
incorporating into DNA in place of normal bases.
b.
inserting into the DNA helix.
c.
modifying the structure of DNA bases.
d.
increasing the number of certain trinucleotide repeats.
e.
causing nucleotide insertions.
12. Frameshift mutations
a.
cause a change in the reading frame of mRNA codons.
b.
are usually caused by base analogs.
c.
usually occur because of radiation exposure.
d.
cause a single amino acid change in the polypeptide chain.
e.
are usually the result of damage caused by free radicals.
13. Free radicals
a.
form because of radiation exposure.
b.
form due to base analogs.
c.
form when atoms have paired electrons.
d.
are not reactive.
e.
are incorporated into DNA instead of normal bases.
14. Free radicals
a.
only cause frameshift mutations.
b.
form due to base analogs.
c.
form when atoms have unpaired electrons.
d.
are not reactive.
e.
are incorporated into DNA instead of normal bases.
15. Mutations
a.
are always easy to detect.
b.
always occur in genes.
c.
show up at a rate of about 6-7 mutations per child born.
d.
are usually only detected when there is a change in phenotype.
e.
are always harmful to an individual.
16. The mutation rates for different genes are affected by several factors. Which of the following
statements about mutation rates for different genes is FALSE?
a.
Gene size affects mutation rates for genes.
b.
Nucleotide repeats found in some genes can increase in number with each generation.
c.
Genes with many adjacent A/T base pairs often have a high mutation rate.
d.
The smaller the gene, the lower the mutation rate.
e.
Nucleotide composition does not affect mutation rates of genes.
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17. Types of mutations include all of the following EXCEPT
a.
single nucleotide substitutions.
b.
insertions.
c.
deletions.
d.
trinucleotide repeats.
e.
methylation of DNA.
18. Which of the following statements about DNA repair is TRUE?
a.
All of the mistakes made in DNA replication are fixed by the proofreading activity of
DNA polymerase.
b.
There is only one DNA repair system in humans.
c.
All mutations are detected and fixed by DNA repair systems.
d.
DNA repair systems recognize distortions in the DNA double helix.
e.
There is no DNA repair system to deal with damage caused by exposure to ultraviolet
light.
19. A cell that has accumulated a lot of mutations can have any of the fates below EXCEPT
a.
undergoing apoptosis.
b.
entering senescence.
c.
becoming cancerous.
d.
undergoing apoptosis then become cancerous.
e.
remaining in a dormant state.
20. Epigenetics involves changes in
a.
the sequence of DNA.
b.
the expression of genes.
c.
the base pairing in the DNA helix.
d.
DNA repair systems.
e.
DNA replication.
21. Epigenetic changes
a.
results in unstable phenotypes.
b.
requires DNA mutations.
c.
are due to distortions in the DNA helix.
d.
can be dependent on whether the promoter regions for genes are available for RNA
polymerase.
e.
are the same for all cells in an individual.
22. Methylation of cytosines in CpG sequences
a.
is the result of damage from free radicals.
b.
does not affect gene expression.
c.
is caused by base analogs.
d.
leads to the insertion of extra base pairs in DNA.
e.
can silence genes.
Chapter 6—Changes in DNA: Mutations and Epigenetics
23. Genetic imprinting
a.
is due to DNA mutations.
b.
affects all genes.
c.
assures that both the maternal and paternal copies of each gene are expressed.
d.
is due to epigenetic changes.
e.
has not been seen in any genetic disorder.
24. Which of the following statements about epigenetics is TRUE?
a.
Epigenetic changes occur because of DNA mutations.
b.
Epigenetic changes are only due to genetic factors.
c.
Epigenetic changes alter the replication of DNA.
d.
Epigenetic modifications can be caused by environmental factors..
e.
Epigenetic drugs are widely used to treat many genetic disorders.
25. Beckwith-Wiedemann syndrome (BWS) is caused by
a.
abnormal genetic imprinting of two small clusters of genes on chromosome 11.
b.
mutations in several genes on chromosome 11.
c.
expression of only the maternal copies of all of the genes on chromosome 11.
d.
expression of only the paternal copies of all of the genes on chromosome 11.
e.
damage to chromosome 11 due to radiation exposure.
TRUE/FALSE
1. Mutations are changes in DNA sequence.
2. Mutations only occur in body cells.
3. Mutations in germ cells are an underlying cause of many types of cancers.
4. The radiation doses that most people are exposed to are measured in rems.
5. An average American undergoes a full-body CAT scan. This does not have much of an effect on their
annual radiation dose.
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6. Base insertions usually lead to frameshift mutations.
7. The main source of radiation exposure for most of the U.S. population is exposure to cosmic radiation.
8. All mutations are harmful.
9. Some mutations can provide an advantage to those who carry them.
10. Each child is born with 65-70 newly-mutated genes.
11. Epigenetics is the study of DNA mutations.
12. Epigenetic modifications alter the regulation of gene expression.
13. Gene promoters that are tightly wound around a histone complex are easily accessible for RNA
polymerase.
14. Methylation within the region of a promoter increases expression of that gene.
MATCHING
Match the associated terms.
a.
genome
b.
millirem
c.
apoptosis
d.
histones
e.
free radical
f.
imprinting
g.
proofreading
h.
mutation
i.
methylation
j.
frameshift
k.
senescence
1. dormant cell
2. Beckwith-Wiedemann syndrome
3. unit of measure of radiation dose
4. unpaired electrons
5. CpG sequences
6. individual’s complete genetic information
7. DNA polymerase
8. change in DNA sequence
9. cell suicide
10. nucleosomes
11. shift in reading frame
ESSAY
1. Cite examples of how nucleotide repeats can cause genetic disorders. How does the number of repeats
relate to the severity of the disorder?
Chapter 6—Changes in DNA: Mutations and Epigenetics
2. What is epigenetics? Describe two epigenetic modifications. What is the effect of epigenetic
modifications on the DNA sequence?
SHORT ANSWER
1. Why it is often difficult to diagnose fetal alcohol syndrome (FAS)? What additional measures are
usually taken before a diagnosis is made?
2. How does radiation exposure from dental x-rays compare to our average annual dose from background
radiation? What is the average total radiation dose in the United States?
3. Explain the difference between mutations that occur in body cells compared to mutations that occur in
germ cells.
4. Explain how each of the following mutagens cause mutations. What are the most common types of
mutations caused by each mutagen?
a. base analogs
b. nitrates
c. chemicals in some pesticides