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Chapter 18 Practice Exam
Terms in this set (34)
The type of mutation that reverses the effects of a frameshift mutation without changing the frameshift and occurs with the same gene as the frameshift is called a(n)
A. intergenic suppressor mutation
B. nonsense mutation
C. missense mutation
D. intragenic suppressor mutation
E. silent mutation
How do germ-line mutations differ from somatic mutations?
a. Germ-line mutations involve small changes to DNA such as base-pair substitutions, while somatic mutations usually involve large deletions.
b. Germ-line mutations occur during DNA replication, while somatic mutations do not.
c. Germ-line mutations result in mutant gametes, while somatic mutations do not.
d. Germ-line mutations are reversible, while somatic mutations are not.
e. Germ-line mutations result in cancers, while somatic mutations do not.
Which of the following base changes in DNA is an example of a transition?
Which of the following correctly describes nonsense mutations?
A. They cause a nonfunctional amino acid to replace a functional amino acid.
B. They change the nucleotide sequence of a gene but do not change the sequence of the resulting protein.
C. They result in the insertion or deletion of a small number of nucleotides to the DNA.
D. They convert a codon for a particular amino acid within a gene into a stop codon.
E. They cannot revert or back mutate to wild-type.
Assume that a base-pair substitution mutation converts a DNA triplet (AAT) to another DNA triplet (AAA). A second mutation now changes the AAA triplet to the GAA triplet. (UUA and CUU code for leucine and UUU codes for phenylalanine.) This second mutation is an example of a(n)
b. intragenic suppressor.
c. loss-of-function mutation.
d. intergenic suppressor.
An example of a genetic disorder in humans that results from a loss-of-function mutation is
a. cystic fibrosis.
c. Huntington disease.
d. myotonic dystrophy.
e. None of the above is correct.
Which of the following statements about somatic mutations is FALSE?
a. Some may give rise to cancers in humans and other animals.
b. They may be inherited by daughter cells after cell division.
c. They may result in inactive gene products of the mutated genes.
d. They may result from both frameshift and base-pair substitution mutations.
e. They may be inherited in the offspring of mutated individuals.
Fragile-X syndrome is an example of a disease caused by what type of mutation?
a. Nonsense mutation
b. Frameshift mutation
c. Expanding nucleotide repeat
Which of the following types of mutations does NOT lead to a change in the amino acid sequence of the gene product?
Insertion or removal of one or more nucleotide base pairs in DNA within a gene often results in a ____________ mutation.
A _________ mutation changes a codon that specifies an amino acid into one that terminates translation.
__________ mutations produce new activities and are usually dominant.
Which of the following kinds of mutations is most likely to be null loss-of-function?
Which of the following statements about an animal bearing a somatic mutation is TRUE?
a. Some, but not all, of the animal's offspring will also carry the mutation.
b. All of the animal's offspring will carry the mutation.
c. Both the animal and its offspring will show the mutant trait.
d. The animal but not its offspring can be affected by the mutation.
e. The gametes produced by the animal will all carry the mutation.
A mutation that changes a GC base pair to AT is a(n)
c. induced mutation.
d. missense mutation.
e. synonymous mutation.
Huntington disease can strike at an earlier age and bring about a more rapid degeneration and death in successive generations within a family. This phenomenon can be explained by which mechanism?
a. Presence of a transposable element in the gene
b. Chronic exposure to mutagens in the environment
c. Expansion of a trinucleotide repeat in the coding sequence of the gene
d. Presence of an extra chromosome in the germ line
e. Absence of a gene product that is involved in DNA repair
What is the consequence of a transversion mutation in duplex DNA?
a. A purine is replaced by a pyrimidine, and a pyrimidine is replaced by a purine.
b. A base pair is lost within the DNA of a gene, which causes a reading frame shift.
c. A purine is replaced by another purine, and a pyrimidine is replaced by another pyrimidine.
d. A base pair is added to the DNA within a gene, which causes a reading frame shift.
e. The sequence of the DNA remains the same since the change involves proteins.
Suppose a research study shows that people who suffer from severe depression are homozygous for a mutation in the hypothetical DEP gene. Individuals without this form of depression have the following sequence at the beginning of the translated region of their DEP genes 5¢-ATG ACG TTT GAA ATT CAG TCT AGA-3¢ (Met Thr Phe Glu Ile Gln Ser Arg). Affected individuals have the following sequence 5¢-ATG ACG TTT GAA ATT TAG TCT AGA-3¢ (Met Thr Phe Glu Ile STOP). The mutation identified is most likely a
b. gain of function.
21. Helen has type I osteogenesis imperfecta (OI), a genetic skeletal disorder. Shown below is her DNA sequence for a portion of the coding region of the collagen type I gene, which contains the mutation responsible for her disorder. The corresponding wild-type sequence is shown also (only one DNA strand is shown in each case).
What type of mutation does Helen carry?
Assume that during DNA replication in a bacterium a mistake is made and a G is inserted into the newly synthesized DNA strand opposite a T in the template DNA strand. If this mistake is not repaired before the next round of DNA replication, what mutation will eventually result?
A) A-to-G base substitution
B) A-to-C base substitution
C) A-to-T base substitution
D) G-to-A base substitution
E) C-to-A base substitution
Ultraviolet light causes what type of DNA lesion?
A) Large deletions
B) Deaminated cytosines
C) Pyrimidine dimers
D) Mismatch bases
Practically all transposable elements that have studied are associated with which of the following?
A) Indirect repeats at each end
B) A gene for transposase
C) A gene for reverse transcriptase
D) A gene for RNA polymerase
E) Flanking direct repeats
Bacterial insertion sequences encode which of the following gene products?
A) Reverse transcriptase
B) DNA polymerase
Transposable elements are found
A) mainly in higher plants.
B) mainly in animals, particularly in mammals.
C) mainly in eukaryotes.
D) mainly in prokaryotes.
E) in practically all organisms.
Which of the following is characteristic of retrotransposons?
A) They use transposase to transpose to new sites.
B) They have inverted repeats at each of their ends.
C) They transpose through an RNA intermediate
D) They make transposase.
E) They are found only in prokaryotes.
Upon transposing to a new site, transposable elements
A) add methyl groups to bases of the surrounding DNA.
B) delete about 100 base pairs of DNA on each side of them.
C) duplicate their transposase gene.
D) express a gene that confers sensitivity to some common antibiotics.
E) create a duplication of a target sequence on each side of them.
Which of the following describes the possible parasitic nature of transposable elements?
A) Transposable elements can increase in number within genomes without providing an advantage to the host.
B) Transposable elements are collected within their genomes by host organisms so that the host will benefit, but not the transposable elements.
C) Transposable elements will provide an evolutionary advantage to host organisms by transposing as often as possible.
D) Transposable elements will enhance their expression of transposase so that the hosts can evolve more quickly.
E) Transposable elements will add methyl groups to their own DNA to reduce their own rate of transposition.
Which of the following characterizes the mode of transposition of retrotransposons?
A) It involves a RNA intermediate.
B) It involves the initial synthesis of transposase.
C) It involves the production of a protein repressor.
D) It only occurs in nondividing host genomes.
E) It requires inverted repeats at each end of the retrotransposon.
Transposition can involve exchange of DNA sequences and recombination, which often leads to DNA
A transposable element is found to use RNA as an intermediate in transposition. On the basis of this information, which of the following would you expect to be correct?
A) The transposable element also probably makes transposase.
B) The transposable element may encode a reverse transcriptase.
C) The transposable element is probably located in a bacterial genome.
D) The transposable element probably contains inverted repeats at each end.
E) The transposable element will not be able to transpose without a second copy also present in the genome
Which of the following pairs of sequences would you expect to be found in the same transposable element?
A) Inverted repeats and a gene for transposase
B) Long terminal repeats and a gene for transposase
C) Inverted repeats and a gene for reverse transcriptase
D) A gene for transposase and a gene for reverse transcriptase
E) Both B and C are both correct.
What is the function of DNA glycosylases?
A) Recognize and cleave phosphodiester bonds in DNA
B) Recognize and remove modified bases from the sugar component of DNA
C) Reattach the two parts of DNA that result from double-strand breaks
D) Remove pyrimidine dimers from DNA of E. coli that result from exposure to UV light
E) Prevent strand slippage during DNA replication
The disorder xeroderma pigmentosum is associated with a defect in what type of DNA repair system?
A) Mismatch repair
B) Base-excision repair
D) Nucleotide-excision repair
E) Homologous recombination
Which of the following enzyme activities is not a part of nucleotide-excision repair?
A) DNA polmerase
B) DNA ligase
C) Reverse transcriptase
D) DNA helicase
E) All of the above are part of nucleotide-excision repair.
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