Deck 11: Gene Mutation, Dna Repair, and Homologous Recombination

Question 1

Which type of mutation converts a nucleotide to an alternative structure with the same composition but a slightly different placement of rare, less stable hydrogen bonds that cause base- pair mismatch?

A) deamination
B) transversion
C) depurination
D) transition
E) tautomeric shift

Answer 1

E

Question 2

A mutant DNA polymerase that increases the frequency of strand slippage would increase the frequency of which type of mutation?

A) splice site
B) transposition
C) transition
D) missense
E) triplet- repeat expansion

Answer 2

E

Question 3

Given the sequence of triplet codons: 5'- TAC AAA ATA CAG CGG- 3', which of these sequences represents a missense mutation?

A) 5'- TAC AAG ATA CAG CGG- 3'
B) 5'- TAC AAA ATA CAC CGG- 3'
C) 5'- TAC AAA ATA CAG AGG- 3'
D) 5'- TAC AAA TAC AGC GGG- 3'
E) 5'- TAG AAA ATA CAG CGG- 3'

Answer 3

B

Question 4

In eukaryotes, homologous recombination is initiated by .

A) Spo11 generating double- stranded DNA breaks
B) Rad51 generating double- stranded DNA breaks
C) p53 generating single- stranded DNA breaks
D) RecA, RecB, and RecC generating single- stranded DNA breaks
E) ATM signaling double- stranded DNA breaks

Question 5

Which of these statements best describes gene expression in a damaged cell?

A) In a damaged cell, p53 is low and BAX transcription is inactive, so Bcl- 2 represses apoptosis.
B) In a damaged cell, p53 is high and BAX transcription is active, so Bcl- 2 is repressed and apoptosis is induced.
C) In a damaged cell, p53 is high and BAX transcription is inactive, so Bcl- 2 is activated and apoptosis is induced.
D) In a damaged cell, p53 is low and BAX transcription is active, so Bcl- 2 is repressed and apoptosis is induced.
E) In a damaged cell, p53 is low and BAX transcription is active, so Bcl- 2 represses apoptosis.

Question 6

You have conducted an Ames test on a given compound. Which of the following would be classified as a positive result on the Ames test?

A) his+ strain grows on an his+ plate.
B) his- strain grows on an his+ plate.
C) his- strain grows on an his- plate.
D) his+ strain grows on an his- plate.
E) his+ strain grows on either an his- or an his+ plate.

Question 7

Transposons can integrate into the promoters of genes, what is the most likely outcome of such an event?

A) amino acid substitution
B) altered gene expression
C) deamination
D) frame shift
E) point mutation

Question 8

You would like to induce a transversion mutation into a sequence of DNA. Which type of chemical mutagen would give you the best chance of inducing the correct mutation without causing transition mutations as well?

A) oxidative agent
B) deaminating agent
C) base analog
D) intercalating agent
E) alkylating agent

Question 9

Which type of mutation is possible due to the redundant nature of the genetic code?

A) nonsense
B) silent
C) splice site
D) frameshift
E) missense

Question 10

If one Holliday junction region is resolved by an NS cut and the other by an EW cut, the resulting chromosomes .

A) are nonrecombinant and carry the combinations A1 and B2 or A2 and B1
B) are recombinant and carry the combinations A1 and B1 or A2 and B2
C) are recombinant and carry the combinations A1 and B2 or A2 and B1
D) are nonrecombinant and carry the combinations A1 and B1 or A2 and B2
E) are A1 and A2 or B1 and B2

Question 11

What type of mutation is seen here? Wild type: 5'- TAC AAA ATA CAG CGG- 3' Mutation: 5'- TAC AAG ATA CAG CGG- 3'

A) transition
B) insertion
C) transversion
D) deletion
E) nonsense

Question 12

Studies of gene mutation frequencies have shown that .

A) mutation frequencies are consistent between organisms, and each region of DNA is equally susceptible to random mutations
B) mutations are rare, and genomes are generally stable
C) mutation are common and adaptive
D) mutations affect RNA, but do not change DNA sequence
E) mutations occur only at certain nucleotides and not others

Question 13

Which enzyme is required to mobilize transposons of any type?

A) transposase
B) reverse transcriptase
C) terminal inverted repeats
D) telomerase
E) RNA helicase

Question 14

A strain of E. coli is unable to use the UV repair pathway because of an apparent absence of DNA helicase activity. Which UV repair gene is likely mutated in this strain?

A) uvr- C
B) uvr- B
C) pol I
D) uvr- D
E) uvr- A

Question 15

What phenotype would you expect to see in a strain of E. coli with a mutation in the phr gene?

A) increase in the methylation of nucleotide bases
B) decrease in UV- induced mutations
C) decrease in reversion of base- pair substitution mutations
D) increase in UV- induced mutations
E) decrease in the methylation of nucleotide bases

Question 16

Which of the following statements is true of non- homologous end joining (NHEJ)?

A) it is error- prone
B) it is a double- strand repair pathway
C) it is error- free
D) it is both error- prone and is a double- strand repair pathway
E) it utilizes the sister chromatid as a template for repair

Question 17

Which of the following is able to cause a change in a reading frame?

A) missense
B) transversion or missense
C) transition
D) deletion
E) transversion

Question 18

Which pathway is affected by an inherited mutation in the ATM gene?

A) nucleotide excision repair pathway
B) reactivation repair pathway
C) photoreactivation
D) UV repair pathway
E) p53 repair pathway

Question 19

Given the sequence of triplet codons: 5'- TAC AAA ATA CAG CGG- 3', which of these sequences represents a nonsense mutation?

A) 5'- TAC AAA ATA CAG AGG- 3'
B) 5'- TAC AAA ATA CAC CGG- 3'
C) 5'- TAG AAA ATA CAG CGG- 3'
D) 5'- TAC AAA TAC AGC GGG- 3'
E) 5'- TAC AAG ATA CAG CGG- 3'

Question 20

The fluctuation test allowed Luria and Delbruck to conclude that .

A) mutations are common and thus allow natural selection
B) mutations occur in the absence of environmental challenges
C) mutations occur at random in response to environmental challenges
D) chemical mutagens are present even in drinking water
E) none of the above

Question 21

Which type of mutagen has a structure similar to one of the DNA nucleotides and therefore can work its way into DNA, where it pairs with a nucleotide?

Question 22

Which type of double- stranded break repair would you expect to be used by a cell in the G1 phase of the cell cycle?

Question 23

What type of mutagen would you use if you wanted to study the effect of pyrimidine dimers in causing cancer?

Question 24

If you have screened 100,000 pollen grains and identified 5 mutants, what is the mutation frequency?

Question 25

Huntington's disease is caused by what kind of mutation?

Question 26

What are three genes that are usually encoded by retrotransposons?

Question 27

What are the two basic types of base- pair substitutions?

Question 28

are structures that have the same composition and general arrangement but a slight difference in bonding and placement of a hydrogen.

Question 29

Which mechanism can be used to repair UV damage in Drosophila but not in humans?

Question 30

DNA glycosylase inhibitors are used to study which DNA repair mechanism?

Question 31

Localized mutations that occur at a specific location, rather than over a larger span on a gene are better known as what?

Question 32

You have developed a new drug and have been asked to test the drug's mutagenicity before putting it on the market. Which test could you use to determine your compound's mutagenic potential?

Question 33

How can the Ames test distinguish mutagens that cause small insertions/deletions from those that cause base substitutions?

Question 34

The alkylating agent nitrosoguanidine adds methyl groups to nucleotide bases and is repaired by which enzyme that removes the added methyl group and restores nucleotides to their normal form?

Question 35

What is the purpose of using liver enzyme (S9 extract) in the Ames test?

Question 36

What process, which is responsible for many trinucleotide repeat disorders, alters the number of DNA repeats?

Question 37

You use several model organisms in your lab's research. Which of your model organisms would you expect to exhibit a higher mutation frequency: E. coli, D. melanogaster, or M. musculus?

Question 38

A second- site mutation that compensates for the mutation in one gene by mutating a second gene and restoring the wild- type phenotype is also known as a mutation.

Question 39

What type of mutation commonly affects CpG islands, altering promoter regions of mammalian genes?

Question 40

What term describes a gene or region of a genome where mutations occur much more often than average?

Question 41

You are interested in studying the function of a gene, so you decide to create point mutations to help you identif important residues in the encoded protein.
In the following set of triplet codons, two nucleotides are underlined, which nucleotide should be mutated to ach your goal and why?
5'- ATG CCC TGG AAC CTG- 3'

Question 42

Double- strand breaks cause genomic instability and are thus potentially lethal to cells. They also greatly increase the risk of cancer and the chance of chromosome structural mutations. Compare and contrast the two mechanisms of double- strand break repair. Why would one mechanism be used over another?

Question 43

A manufacturer of nutritional supplements proposes to sell extracts from an Antarctic algae as an ingestible remedy for sleep disorders. Your task is to determine if this extract may be mutagenic, how do you test this?

Question 44

The Ames test is designed to identify the rate of that restore the ability of bacteria to synthesize their own histidine, thus eliminating the need for histidine supplementation of the growth medium.

Question 45

When a DNA mismatch is detected in E.coli, what mechanism allows the cell to determine which was more likely to be the original nucleotide?

Question 46

Retrotransposons are unique among transposable elements in that they require the enzyme
for mobilization?

Question 47

Describe a hypothetical result of the fluctuation test that would have supported the hypothesis that mutations occur in response to environmental challenge, and explain how this result was different from the observed result described in the chapter?

Question 48

The 'activator' transposable element Ac encodes the enzyme which can cause the mobilization of the 'dissociation' element Ds?

Question 49

You accidentally exposed your cell culture dish to radiation, but you are not sure of the precise wavelength of the exposure. How can you use the induced DNA damage to tell whether the radiation was UV or higher energy? What is the difference between the DNA damage caused by UV radiation compared to higher- energy radiation? Which type of damage is likely to be the most lethal to your cells?

Question 50

Which bases would you mutate to create a nonsense transition mutation?
5'- ATG GGA TGG CAC CTG- 3'

Question 51

DNA damage signaling processes are essential for regulating the transition within the cell cycle.

Question 52

Agents generating mutation- inducing DNA damage are collectively referred to as
.