Exam 2 study questions
42. The deamination of ___ produces mismatched thymines in DNA.
5-methylcytosine
37. During replication, proofreading of the newly synthesized DNA is performed by
DNA polymerase
14. Spontaneous mutation rates are greatly reduced by
DNA repair mechanisms
47. Which strain of bacteria is used in the Ames test for chemical mutagenicity?
Salmonella typhimurium
46. Which of the following is an example of a nonsense mutation?
UAC to UAG
44. In the absence of repair mechanisms, DNA mutates considerably from spontaneous and induced sources. This mutation rate is evident from people afflicted with compromised repair mechanisms, who suffer from
Xeroderma pigmentosum
21. An IS (insertion sequence) element contains
a transposase gene and inverted repeats at the ends.
20. In order for the dissociation element (Ds) mutations in corn to be stable,
an Ac element must not be present
7. Which of the following is not mutagenic? a) 5BU b) AZT c) Nitrous acid d) Hydroxylamine e) Acridine
b) AZT
45. The sequence 5'-AUGGGGUGCCAUUUU-3' yields a polypeptide five amino acids long. What base substitution would truncate the polypeptide to only two amino acids?
changing the first cytosine to an adenine
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
e) B,C and D only
12. Mutation frequency is the
number of a specific mutation in a defined population.
18. Nonsense suppressors are usually mutations in genes coding for
tRNA
39. In E. coli, suppressor mutations are often located in genes for
tRNA genes
40. In an Ames test of an unevaluated chemical, numerous bacterial colonies grow on the minimal medium plates. Which of the following conclusions is valid?
the test chemical is mutagenic
29. 5-bromouracil is an analog of which base?
thymine
32. Photolyase functions in
thymine dimer repair
34. A mutation changes an A-T base pair to T-A. This is a ___ mutation
transversion
22. What is conservative transposition?
Movement of transposable elements WITHOUT replication of the element
25. Genetic manipulation in Drosophila may be assisted by the use of
P elements
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?
The reading frame will be shifted to the left, and the wrong amino acids will be added from this point on.
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
a) adenine to guanine
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
b) 5'-AGA-3' to arginine
3. Frameshift mutation 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
e) a mutation that causes an addition or deletion of one or two base pairs in a gene
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
e) all of these
23. Dissociation elements (Ds) in plants are examples of a) activator transposons that can direct their own transposition. b) nonautonomous elements that require activation by an autonomous element. c) mutator genes that increase the spontaneous mutation frequencies of other genes. d) repeated sequences that are targeted by a transposase. e) Both B and C
e) both B and C
31. A ___ mutation may result from the insertion or deletion of a nucleotide.
frameshift
38. Ethidium bromide is a(n) ___ agent
intercalating
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
intergenic suppression
33. A mutation changes a codon for leucine into one that specifies isoleucine. This is a ___ mutation.
missense
48. Which of the following mutations potentially has the greatest effect on gene expression?
mutation in the promoter
35. A mutation occurs in which an AAA codon, which signifies lysine, into AGA, which signifies a chemically similar amino acid, arginine, and has no effect on protein function. This is an example of a ___ mutation.
neutral
24. Which procedure would you use to detect a nutritional mutation in microorganisms?
replica plating
30. A ___ mutation in a gene in amino acid biosynthesis pathway permits the bacterium to once again synthesize the amino acid
reversion
36. A mutation occurs in which an AUU codon is changed to an AUC codon. Both of these codons signify the amino acid leucine. This is a ___ mutation.
silent
10. Thymine dimers are commonly caused by
ultraviolet radiation
9. The deamination of cytosine creates
uracil
26. Choose the best answer. a) LINEs and SINEs are repetitive sequences in humans that can also, as retrotransposons, insert into genes and cause disease. b) Changes in heritable traits result from adaptation to environmental influences. c) Somatic mutations may be inherited by the next generation. d) Both A and B are correct. e) All of the above are correct.
LINEs and SINEs are repetitive sequences in humans that can also, as retrotransposons, insert into genes and cause disease.
1. Nonsense mutation 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
a) A mutation that changes a codon from one that represents an amino acid to one that signals a chain termination
4. Point mutation 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
b) a mutation that causes a change in a single base pair
28. The DNA polymerase proofreading mechanism maintains a low mutation rate a) in eukaryotic genes. b) in prokaryotic genes. c) only in the presence of ionizing radiation. d) Both A and B are correct. e) All of the above are correct.
b) in prokaryotic genes
5. Neutral mutation 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
c) a mutation in a gene that causes no detectable change in the protein
43. The mutation induced most commonly in DNA treated with ultraviolet light is the result of
creation of thymine dimers
2. Missense mutation 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
d) A mutation that changes a codon from one amino acid to another
27. Choose the best answer. a) 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. b) 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. c) A tautomer is an uncommon form of DNA base that naturally exists along with the common form. d) Both A and C are correct. e) All of the above are correct.
d) both A and C are correct
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
d) they may exist in alternate chemical states that pair with different DNA bases than the normal state during replication
41. Nitrous acid induces ___ of bases in DNA.
deamination
11. Xeroderma pigmentosum is a human genetic disease caused by
defective DNA excision-repair mechanisms.