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.