Description
iGenetics A Molecular Approach 3rd Edition Russell Test Bank
ISBN-13: 978-0321569769
ISBN-10: 0321569768
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iGenetics: A Molecular Approach, 3e (Russell/Bose)
Chapter 7 DNA Mutation, DNA Repair, and Transposable Elements
MATCHING
Please select the best match for each term.
- A) A mutation that changes a codon from one that represents an amino acid to one that signals a chain termination
- B) A mutation that causes a change in a single base pair
- C) A mutation in a gene that causes no detectable change in the protein product
- D) A mutation that changes a codon from one amino acid to another
- E) A mutation that causes an addition or deletion of one or two base pairs in a gene
1) Nonsense mutation
Skill: Factual recall
2) Missense mutation
Skill: Factual recall
3) Frameshift mutation
Skill: Factual recall
4) Point mutation
Skill: Factual recall
5) Neutral mutation
Skill: Factual recall
Answers: 1) A 2) D 3) E 4) B 5) C
MULTIPLE CHOICE
6) Which of the following nucleotide changes leads to a transition mutation?
- A) Adenine to guanine
- B) Adenine to cytosine
- C) Guanine to cytosine
- D) Thymine to guanine
- E) Guanine to thymine
Answer: A
Skill: Application of knowledge
7) Which of the following is not mutagenic?
- A) 5BU
- B) AZT
- C) Nitrous acid
- D) Hydroxylamine
- E) Acridine
Answer: B
Skill: Factual recall
8) Base analogs may cause mutations because
- A) they modify the chemical structure and properties of the normal base.
- B) they insert themselves between adjacent bases on the DNA strand and cause an extra base to be inserted during replication.
- C) they remove amino groups from bases, causing them to pair with the wrong base during replication.
- D) they may exist in alternate chemical states that pair with different DNA bases than the normal state during replication.
- E) Both A and C
Answer: D
Skill: Conceptual understanding
9) The deamination of cytosine creates
- A) 5-methyl cytosine.
- B) uracil.
- C) 2-aminopurine.
- D) 5-bromouracil.
- E) thymine.
Answer: B
Skill: Factual recall
10) Thymine dimers are commonly caused by
- A) ultraviolet radiation.
- B) ionizing radiation such as X-rays.
- C) tautomers.
- D) alkylating agents.
- E) intercalating agents.
Answer: A
Skill: Factual recall
11) Xeroderma pigmentosum is a human genetic disease caused by
- A) elevated levels of cholesterol in the blood.
- B) failure to produce pigment that protects the skin cells from UV light exposure.
- C) defective DNA excision-repair mechanisms.
- D) mutations that inactivate tumor suppressor genes.
- E) loss of genes controlling the SOS
Answer: C
Skill: Factual recall
12) Mutation frequency is the
- A) number of mutations per gene per generation.
- B) number of mutations per nucleotide per generation.
- C) number of mutations per cell per generation.
- D) number of a specific mutation in a defined population.
- E) total number of mutations in a defined population.
Answer: D
Skill: Factual recall
13) The codon 5′-AAA-3′ codes for the amino acid lysine. Which of the following mutations in this codon is a neutral mutation?
- A) 5′-ATA-3′ to isoleucine
- B) 5′-AGA-3′ to arginine
- C) 5′-AAG-3′ to lysine
- D) 5′-CAA-3′ to glutamine
- E) 5′-AAC-3′ to asparagine
Answer: B
Skill: Application of knowledge
14) Spontaneous mutation rates are greatly reduced by
- A) exposure to ionizing radiation.
- B) reverse mutations.
- C) base-modifying agents.
- D) DNA repair mechanisms.
- E) performing the Ames test.
Answer: D
Skill: Factual recall
15) A mutation during DNA replication causes a G to be inserted after the first base of the codon for tryptophan. How will this affect the growing polypeptide chain?
- A) It will not be affected.
- B) Elongation will stop prematurely.
- C) There will be a single amino acid substitution.
- D) The reading frame will be shifted to the left, and the wrong amino acids will be added from this point on.
- E) An extra amino acid will be added, but the reading frame will not be affected.
Answer: D
Skill: Reasoning and logic
16) In Drosophila, the wild-type eye color is red. A mutation, vermilion, causes vermilion-colored eyes, unless there is a mutation in another gene, suv, which, when homozygous or hemizygous, results in eyes that are the wild-type red even in the presence of the vermilion mutation. This is an example of
- A) forward mutation.
- B) reverse mutation.
- C) intragenic suppression.
- D) intergenic suppression.
- E) back mutation.
Answer: D
Skill: Application of knowledge
17) A transposon is
- A) a DNA segment that can insert itself at one or more sites in a genome.
- B) a “jumping gene.”
- C) a DNA segment that may cause mutations in genes or chromosomal rearrangements.
- D) a mobile genetic element that may or may not leave a copy of itself in its original site when it moves to a new site.
- E) All of these
Answer: E
Skill: Factual recall
18) Nonsense suppressors are usually mutations in genes coding for
- A) proteins.
- B) enzymes.
- C) mRNA.
- D) tRNA.
- E) rRNA.
Answer: D
Skill: Factual recall
19) Which of the following transposable elements are found in eukaryotes but not in prokaryotes?
- A) IS elements
- B) Families of autonomous and nonautonomous elements
- C) Retrotransposons
- D) Ty elements
- E) B, C, and D only
Answer: E
Skill: Factual recall
20) In order for the dissociation element (Ds) mutations in corn to be stable,
- A) an Ac element must be present.
- B) an Ac element must not be present.
- C) the Ds must contain the gene for transposition.
- D) the DNA must not be replicated.
- E) None of these
Answer: B
Skill: Factual recall
21) An IS (insertion sequence) element contains
- A) a transposase gene only.
- B) a transposase gene and additional genes.
- C) a transposase gene and inverted repeats at the ends.
- D) a transposase gene, additional genes, and inverted repeats at the ends.
- E) genes but not a transposase gene.
Answer: C
Skill: Factual recall
22) What is conservative transposition?
- A) No net increase in the number of transposable elements in the genome.
- B) A net increase in the number of transposable elements in the genome.
- C) Movement of transposable elements with replication of the element.
- D) Movement of transposable elements without replication of the element.
- E) Transposition without disruption of normal gene product activity.
Answer: D
Skill: Factual recall
23) Dissociation elements (Ds) in plants are examples of
- A) activator transposons that can direct their own transposition.
- B) nonautonomous elements that require activation an autonomous element.
- C) mutator genes that increase the spontaneous mutation frequencies of other genes.
- D) repeated sequences that are targeted a transposase.
- E) Both B and C
Answer: E
Skill: Factual recall
24) Which procedure would you use to detect a nutritional mutation in microorganisms?
- A) Visible inspection
- B) Replica plating
- C) Controlled crosses
- D) Isolation at high temperature
- E) Plating on antibiotic-containing medium
Answer: B
Skill: Conceptual understanding
25) Genetic manipulation in Drosophila may be assisted the use of
- A) P
- B) Ty
- C) factor.
- D) bacteriophage Mu.
- E) Tn10.
Answer: A
Skill: Factual recall
TRUE/FALSE
26) LINEs and SINEs are repetitive sequences in humans that can also, as retrotransposons, insert into genes and cause disease.
Answer: TRUE
Skill: Factual recall
27) Changes in heritable traits result from adaptation to environmental influences.
Answer: FALSE
Explanation: Changes in heritable traits result from random mutations.
Skill: Conceptual understanding
28) Somatic mutations may be inherited the next generation.
Answer: FALSE
Explanation: Only germ-line mutations may be heritable; somatic mutations only affect the individual in which the mutation occurs.
Skill: Conceptual understanding
29) 5-bromouracil (5BU) is a mutagen because it is an analog of the base thymine and may pair with guanine instead of adenine if it is incorporated into a DNA strand.
Answer: TRUE
Skill: Factual recall
30) A silent mutation is a change in the DNA sequence that alters the amino acid sequence of the encoded protein but does not change its function.
Answer: FALSE
Explanation: A silent mutation is a change in the DNA sequence that does not change the amino acid sequence of the protein due to the redundancy of the genetic code.
Skill: Factual recall
31) A tautomer is an uncommon form of DNA base that naturally exists along with the common form.
Answer: TRUE
Skill: Factual recall
32) The DNA polymerase proofreading mechanism maintains a low mutation rate in eukaryotic genes.
Answer: FALSE
Explanation: The DNA polymerase proofreading mechanism is found only in bacteria, where it detects the insertion of incorrect bases following DNA replication.
Skill: Conceptual understanding
33) A transposon may carry genes for proteins that enable their transposition as well as genes for other functions such as drug resistance.
Answer: TRUE
Skill: Factual recall
34) Composite transposons contain a central region with genes and repeated sequences at their ends but do not terminate with IS elements.
Answer: FALSE
Explanation: Composite transposons contain a central region with genes flanked at both sides IS elements as well as terminal inverted repeats.
Skill: Factual recall
35) A cointegrate is characteristic of replicative transposition.
Answer: TRUE
Skill: Factual recall
SHORT ANSWER
36) An mRNA codon reads GUA. If a transition mutation occurs at the third base pair, will the final protein be changed?
Answer: Yes. Valine will be inserted in place of an asparagine.
Skill: Application of knowledge
37) A point mutation changes a codon from UCG to UAG. What will happen to the resulting polypeptide?
Answer: UAG is a stop codon, so the polypeptide will terminate prematurely.
Skill: Application of knowledge
38) What are two ways that a reverse mutation can occur?
Answer: A mutation in the same gene can restore the original phenotype, or a suppressor mutation at a second site in the genome can suppress the forward mutation.
Skill: Factual recall
39) How does an intercalating agent such as ethidium bromide cause mutations?
Answer: The substance fits between adjacent bases on one strand of a DNA sequence, causing the complementary strand to be miscopied during replication. This usually results in a frameshift mutation.
Skill: Factual recall
40) How can PCR be used to induce site-specific mutations in DNA?
Answer: Two nested pairs of primers are used, the internal pair having a targeted mismatch that is copied into the newly synthesized DNA fragments. The external primers are used to replicate the mutated fragments.
Skill: Application of knowledge
41) For a particular gene, if one gene in a million experiences a mutation each generation, what is its mutation frequency?
Answer: 10-6
Skill: Application of knowledge
42) A tumor suppressor gene is cloned and mutagenized in vitro, then injected into mouse embryos to create knockout mice. How could you identify the heterozygous knockout mice and create mice susceptible to tumors?
Answer: Reared heterozygous mice can be screened molecularly to identify the ones with the mutation. Interbreeding these mice will result in some homozygous knockout progeny, which in turn will show rapid development of tumors.
Skill: Analytical reasoning
43) Describe how the Ames test is used to determine whether a particular chemical is mutagenic.
Answer: Strains of the bacteria Salmonella typhimurium that are auxotrophic for histidine are plated on a histidine-lacking nutrient agar with rat liver cells. The unknown chemical is added to the agar plate, and the plate is observed for bacterial growth that would indicate reverse mutations caused the chemical resulting in histidine prototrophy.
Skill: Conceptual understanding
44) What kind of mutation-detection procedure can be used to detect the white-eye mutation in Drosophila?
Answer: Screening for this mutation can be done inspection since it is a visible mutation.
Skill: Conceptual understanding
45) How does the nucleotide excision repair (NER) system in E. coli work, and what kinds of DNA damage does it repair?
Answer: The NER system repairs thymine dimers and other serious distortions of the DNA helix. It is a system of four proteins (UvrA, UvrB, UvrC, and UvrD) that work in a complex to recognize a distortion in the DNA, make cuts on either side of the lesion, release the short single-stranded cut segment, and allow DNA polymerase and ligase to fill in the gap with new bases.
Skill: Factual recall
46) Explain how IS elements produce target-site duplications when they move.
Answer: The enzyme transposase makes a staggered cut in the target sequence of the recipient DNA. The IS element is inserted, becoming joined to the single-stranded ends. The gaps are then filled in DNA replication, resulting in a copy of both the IS element and the target sequence.
Skill: Conceptual understanding
47) Barbara McClintock discovered that a controlling element was responsible for the mutant-spotted phenotype (purple spots on white) in corn kernels. Explain how this works.
Answer: A normal C gene produces purple pigment in the corn kernel cells. If this gene is disrupted the transposon Ds (a “mobile controlling element”), no pigment is produced, resulting in a white kernel. Reversions of this mutation can occur if Ds transposes out of the gene during development, resulting in spots of purple pigment on the kernel. The transposition of Ds is controlled an autonomous “activator” element, Ac.
Skill: Conceptual understanding
48) What is a retrotransposon, and how does it differ from typical transposons?
Answer: Most transposons move a DNA-to-DNA mechanism, but retrotransposons (such as yeast Ty elements, Drosophila copia elements, and human LINEs and SINEs) transpose via an RNA intermediate using a transposon-encoded reverse transcriptase.
Skill: Factual recall
49) How was the adaptive method for acquiring mutations disproved?
Answer: Luria and Delbruck argued that if mutations occurred due to exposure to a particular environment, then the number of cells that had the mutation would be similar in different identical populations. However, if the mutations occurred randomly, then the number of cells with that particular mutation would differ or fluctuate in identical populations exposed to the same environmental factor. They proved the second argument to be true infecting identical bacterial cultures with the bacteriophage T1 and counting the number of resistant colonies. The number of resistant colonies fluctuated widely in the different cultures.
Skill: Factual recall
50) Explain what a mutator gene is and give an example.
Answer: A mutator gene is a gene in which a mutation results in a much higher-than-normal mutation frequency for all other genes. For example, mutD mutations in E. coli affect the function of DNA polymerase III. This causes defective 3′-to-5′ proofreading repair activity and results in many incorrectly inserted nucleotides being left unrepaired.
Skill: Conceptual understanding
