Question set 7

Mutations can also occur within the regulatory regions of genes. Fragile X is an example of a disorder caused by one such mutation by increasing the length of the long arm of the X chromosome and ultimately decreasing mRNA stability. What type of mutation causes Fragile X? A splice site B frameshift C triplet-repeat expansion D promoter E polyadenylation

C

Given the DNA sequence 5-TAC AAA ATA CAG CGG-3, which of these sequences represents a frameshift mutation? A 5-TAC AAA ATA CAG AGG-3 B 5-TAC AAG ATA CAG CGG-3 C 5-TAC AAA TAC AGC GGG-3 D 5-TAC AAA ATA CAC CGG-3 E 5-TAG AAA ATA CAG CGG-3

C 5-TAC AAA TAC AGC GGG-3

Which of the following spontaneous changes in DNA structure/sequence generally result from DNA replication errors A Depurination. B Deamination of cytosine. C Expansion of trinucleotide repeat sequences. D Tautomeric shift that changes the structure of a base.

C Expansion of trinucleotide repeat sequences.

Which type of mutation results in a string of altered amino acids at the end of the polypeptide product? A Nonsense. B Silent. C Frameshift. D Missense.

C Frameshift

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 either an his- or an his+ plate. E His+ strain grows on an his- plate.

C His- strain grows on an his- plate.

Given the sequence of a DNA coding strand, 5'-TAC AAA ATA CAG CGG-3', which of these sequences represents a nonsense mutation? A 5'-TAC AAA ATA CAC CGG-3' B 5'-TAC AAA TAC AGC GGG-3' C 5'-TAC AAG ATA CAG CGG-3' D 5'-TAC AAA ATA CAG AGG-3' E 5'-TAG AAA ATA CAG CGG-3'

E 5'-TAG AAA ATA CAG CGG-3'

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

Tautomers

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

hotspots of mutation

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

mutagens

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?

base analog

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

strand slippage

Which type of mutation converts a nucleotide to an alternative structure with the same composition but slightly different placement of hydrogen bonds with a rare, less stable form that causes base-pair mismatch? E deamination A tautomeric shift B transversion C depurination D transition

tautomeric shift

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

transition and transversion

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

5x10−5

Polydactyly is a human autosomal dominant condition that produces extra fingers and toes. Studies of hundreds of families with polydactyly have determined that penetrance for the dominant allele is 70%. Hospital-based surveys of live births find that 1 in 40,000 infants has a new case of polydactyly. Use this information to estimate the mutation rate of the gene. A 1 in 56,000 gametes B 1 in 28,000 gametes C 7 in 800,000 gametes D 7 in 400,000 gametes

A 1 in 56,000 gametes

How is homologous recombination initiated in eukaryotes? A By a double-strand break in one homolog. B By double-strand breaks in both homologs. C By a single-strand break in one homolog. D By single-strand breaks in both homologs.

A By a double-strand break in one homolog.

What are the examples of chemical mutagens? A EMS B hydroxylamine C nitrogen D water

A EMS B hydroxylamine

Which of these statements best describes gene expression in a damaged cell? A In a damaged cell, p53 is high and BAX transcription is active, so Bcl-2 is repressed and apoptosis is induced. B In a damaged cell, p53 is low and BAX transcription is active, so Bcl-2 represses apoptosis. C In a damaged cell, p53 is low and BAX transcription is inactive, so Bcl-2 represses apoptosis. 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 high and BAX transcription is inactive, so Bcl-2 is activated and apoptosis is induced.

A In a damaged cell, p53 is high and BAX transcription is active, so Bcl-2 is repressed and apoptosis is induced.

Which type of DNA damage is repaired by the enzyme photolyase? A Thymine dimers. B Methylated or alkylated bases. C Apurinic sites. D Single-strand breaks in the DNA backbone

A Thymine dimers.

What are the examples of radiant energy that causes mutationS? A UVradiation B IR radiation C microwave irradiation D γ radiation

A UVradiation D γ radiation

The compound 5-bromodeoxyuridine (BrdU) is a derivative of uracil, and if BrdU becomes incorporated during DNA replication, it pairs with adenine. This compound is best classified as which type of mutagen? A base analog B intercalating agent C deaminating agent D oxidative agent E alkylating agent

A base analog

What kind of DNA lesion does UV energy cause? A pyrimidine dimerisation B deamination C induction of DNA strand breaks D frameshift mutation

A pyrimidine dimerisation

Which types of mutation are possible thanks to the redundant nature of the genetic code? A silent B missense C nonsense D frameshift E splice site

A silent

Which of the adenines in the following sequence could you mutate to create a missense transition mutation? 5-ATG GGA TGG CAC CTG-3

A to T or A to C

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?

Ames test

Given the DNA sequence 5-TAC AAA ATA CAG CGG-3, which of these sequences represents a missense mutation? A 5-TAC AAA TAC AGC GGG-3 B 5-TAC AAA ATA CAC CGG-3 C 5-TAC AAA ATA CAG AGG-3 D 5-TAG AAA ATA CAG CGG-3 E 5-TAC AAG ATA CAG CGG-3

B 5-TAC AAA ATA CAC CGG-3

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 insertion B transition C nonsense D deletion E transversion

B Transition

What type of mutation results in a single amino acid substitution? A Silent. B Missense. C Nonsense. D A single nucleotide insertion.

B missense

Identify two DNA repair mechanisms that remove UV-induced DNA lesions. A nonhomologous end joining B photo reactivation C nucleotide excision D synthesis-dependent strand annealing

B photo reactivation C nucleotide excision

Bypass (or translesion) DNA polymerases in E. coli are unique in their ability to do which of the following? A Synthesize DNA in the 3' - 5' direction. B Remove nucleotides using a 3' - 5' exonuclease activity. C Replicate across DNA damage that stalls DNA pol III. D Synthesize long stretches (100's of nucleotides) of DNA.

C Replicate across DNA damage that stalls DNA pol III.

The Ames Test is used to determine the potential mutagenicity of test compounds by screening for new mutations is which of the following organisms? A Mouse. B Escherichia coli. C Salmonella typhimurium. D Yeast.

C Salmonella typhimurium.

What kinds of gene mutations are induced by radiation energy? A transversions B transitions C all of the above

C all of the above

Thymine dimers are most commonly caused by which of the following? A DNA intercalating agents. B X-rays. C Alkylating agents. D U.V. irradiation.

D U.V. irradiation

What kinds of gene mutations are induced by chemical mutagens? A frameshifts B transversions C transitions D all of the above

D all of the above

An intercalating agent such as aflatoxin is more likely to cause which type of mutation? A transition B transversion C depurination D frameshift E deamination

D frameshift

Studies of gene mutation frequencies have shown that A) mutations are rare, and genomes are generally stable. B) mutation frequencies differ among organisms and also between genes, suggesting certain genes are more susceptible to mutation. C) mutation frequencies are consistent between organisms, and each region of DNA is equally susceptible to random mutations. D) Both A and B are correct. E) Both A and C are correct.

D) Both A and B are correct.

The adaptation mutation hypothesis predicts that: A environmental change cannot trigger mutations in a specific gene. B separate bacterial cultures may contain different frequencies of a particular gene mutation. C mutations occur at random in organisms. D bacterial cultures exposed to multiple types of environmental stress will consistently resist mutation. E different bacterial cultures exposed to the same stress will have similar frequencies of a particular mutation.

E different bacterial cultures exposed to the same stress will have similar frequencies of a particular mutation.

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

G to A