CH. 7 - Mutations and CH 8.1 Questions

Choose all features of T4 phages with rII— mutations. Multiple select question. a) They produce larger plaques than normal, with sharper edges. b) They infect both E. coli B strains and E.coli K(λ) strains. c) They infect E. coli B strains, but not E.coli K(λ) strains. d) They infect E.coli K(λ) strains, but not E. coli B strains. e) They produce smaller plaques than normal, with more irregular edges.

a and c

If the proofreading ability of DNA polymerase fails and it inserts the wrong base, which of the following is most likely to be able to fix the resulting mutation? Multiple choice question. a) Nonhomologous end-joining b) Base excision repair c) Methyl-directed mismatch repair d) Nucleotide excision repair e) Homologous recombination repair

c) Methyl-directed mismatch repair

Deletion of a nucleotide in a protein-coding region during DNA replication Multiple Choice a) causes one amino acid of the protein to be incorrect. b) has no effect on the resulting protein.causes all of the amino acids of the protein to be incorrect. c) causes the amino acid sequence encoded after the deletion to be incorrect. d) causes the amino acids encoded before the deletion to be incorrect.

c) causes the amino acid sequence encoded after the deletion to be incorrect.

In a tautomeric shift, a) carbon atoms move to form a base with altered properties. b) it is always adenine that is changed.adenine is changed so it can no longer form base pairs. c) hydrogen atoms move to form a base with altered hydrogen bond formation properties. d) bonding of bases ultimately remains unchanged.

c) hydrogen atoms move to form a base with altered hydrogen bond formation properties.

Benzer hypothesized that if a gene is made of separately mutable subunits, then recombination between those subunits should be possible within the gene. Based on this, he predicted that crossing-over between homologous chromosomes carrying different mutations in the same gene _____. Multiple choice question. a) should be able to frequently generate a wild-type allele b) should never generate a wild-type allele c) should be able to generate a wild-type allele, even if very rarely

c) should be able to generate a wild-type allele, even if very rarely

A single point mutation can affect many genes

False - affect one or a few base pairs in the DNA sequence and thus alter only one gene at a time.

ch 8.1 What incorrect concept was ruled out by the results of Benzer's rII gene recombination experiment? Multiple choice question. a) A gene is a single unit that can be mutated in only one way. b) Recombination can occur within a gene. c) A gene can function only if all portions are wild-type. d) A gene has different parts that can each mutate.

a) A gene is a single unit that can be mutated in only one way.

In polyQ trinucleotide repeat expansion disorders, the repeat sequence is _____. Multiple choice question. a) CGG b) ATG c) CAG d) TAG e) CTG

c) CAG

fig. 8.2a On this image, which letter(s) represent(s) complementation? Multiple choice question. B Both A and B (each shows a different type of complementation) A

for A: m1 and m2 defecctive (mutant recessive) alleles are on different genes (m1 on gene G and m2 on Gene R) so offspring will have wild type phenotype becuz maternal Xmsome supplies gene R function while paternal Xmsome supplies gene G function For B: m1 and m2 defective alleles located on same gene G in both maternal and paternal Xmsomes so mutant phenotype expressed in offspring for gene G....aka no functioning gene G

Alkylating agents covalently attach ______________ or __________ groups to DNA bases, and thus disrupt their normal base pairing properties

methyl ethyl

A system in bacteria that uses methyl groups on the parental DNA strand to determine which of two noncomplementary bases is correct.

methyl directed mismatch repair

On a plate of E. coli, the round clear areas that are sites of phage infection events are known as __________

plaque

A temporary change in the structure of a nitrogen base due to movement of hydrogen atoms is called a(n) __________________

tautomerization

1) 5-Bromouracil -------> Is incorporated into DNA instead of thymine, but can pair with guanine 2) Hydroxylamine ------> Adds -OH to cytosine, allowing it to pair with adenine. 3) Ethylmethane sulfonate -------> Adds an ethyl group to guanine, which then pair incorrectly 4) Nitrous acid ---------> Deaminates cytosine and adenine, changing their pairing properties 5) Proflavin --------> Intercalates into the double helix, causing deletions and insertions

1) base analog 2) hydroxylating agent 3) alkylating agent 4) deamination agent 5) intercalating agent

One type of error-prone DNA repair involves "sloppy" DNA polymerases that are attracted to stalled replication forks where they add random nucleotides. This type of DNA repair is known as the ____________ system.

SOS system

When changes in DNA appear, they are initially considered "potential" mutations. Why? Multiple choice question. a) Because most of them are lethal b) Because most of them are repaired before the altered DNA is replicated c) Because most of them are repaired after the altered DNA is replicated

b) Because most of them are repaired before the altered DNA is replicated

A mutation that removes an adenine or guanine from the DNA is known as a ______. Multiple choice question. a) decarboxylation b) depurination c) deamination d) depyrimidination

b) depurination

Certain compounds have a structure similar to normal DNA bases and so can be incorporated into daughter strands during DNA replication. These compounds are called ________________

base analogs

What is one of the main determinants of the mutation rate of a particular gene? Multiple choice question. a) The G+C content of the gene b) Hydrophobicity of the protein product c) Length of the coding sequence d) Which chromosome it is on

c) Length of the coding sequence

In Benzer's recombination experiment, the indication that recombination had occurred within the gene was _____. Multiple choice question. a) lack of plaques on E. coli K(λ) b) lack of plaques on E. coli B c) formation of plaques on E. coli K(λ) d) formation of plaques on E. coli B

c) formation of plaques on E. coli K(λ)

A researcher is studying the rII locus of phage T4. Three rII-- strains are obtained: A, B, and C. E. coli strain K(λ) is coinfected with two rII− strains simultaneously and the results are recorded. Infection with A and B phage = lysis occurs Infection with A and C phage = lysis occurs Infection with B and C phage = no lysis occurs What can be inferred from this complementation test? Multiple Choice a) Strains A and B have mutations in the same gene, and strain C has a mutation in a different gene. b) Strains A, B, and C have mutations in three different genes. c) Strains A, B, and C have mutations in the same gene. d) Strains A and C have mutations in the same gene, and strain B has a mutation in a different gene. e) Strains B and C have mutations in the same gene, and strain A has a mutation in a different gene.

e) Strains B and C have mutations in the same gene, and strain A has a mutation in a different gene. we dont know what the wildtype phenotype is but we can infer that either lysis or no lysis is wild-type outcome and so: answer d) wud be close to correct except that if strain A and C have same gene and causes lysis and when Strain A and B are paired together causes lysis too so A and B would be on same gene too instead of different genes like answer is saying so thats why its incorrect answer c wud be correct only if no lysis occured on all 3 pairings answer b wud be correct if lysis occured on all 3 pairings answer a wud be correct if no lysis occured between A and C and B and C

A region of DNA has six copies of a trinucleotide repeat. During one round of replication, the template strand slips as shown in the diagram. How many repeats will the DNA have if the newly synthesized strand is used as a template in the next round of replication? a) 4 b) 10 c) 2 d) 8 e) 6

a) 4

ch 8.1 Which experiment most strongly contradicts the notion of genes as unitary "beads on a string"? Multiple choice question. a) Benzer's recombination experiment with phage rII genes b) The Luria-Delbruck fluctuation experiment c) Measures of spontaneous mutation rates for coat color genes in mice d) The Ames test showing reversion of his- mutants

a) Benzer's recombination experiment with phage rII genes

A genetic screen identified several fly strains homozygous for independent mutations. All of the strains have a similar short-wing mutant phenotype. Is the same gene mutant in all of the strains? Multiple choice question. a) Cannot be determined without further testing. b) No -- since they arose independently they are mutations in different genes. c) It depends on how big the gene is. d) Yes -- since they have the same phenotype they all have mutations in the same gene.

a) Cannot be determined without further testing.

What accounts for the low error rate in DNA replication? Multiple choice question. a) The polymerase has a 3'-to-5' exonuclease. b) Due to the nature of nucleotide base-pairing, incorrect nucleotides cannot be inserted. c) The cell increases antioxidant levels during replication. d) DNA polymerase discards the copy if a wrong base is inserted, and starts over.

a) The polymerase has a 3'-to-5' exonuclease.

Alkylating agents cause mutations by _____. Multiple choice question. a) adding methyl or ethyl groups that disrupt base pairing b) creating thymine dimers that block DNA replication c) forming free radicals that damage DNA structure d) being incorporated instead of normal bases during DNA replication

a) adding methyl or ethyl groups that disrupt base pairing

picture of two e coli cells 1 ecoli cell has m1 and m2 defective alleles on same gene in both maternal and paternal chromosomes 2nd ecoli cell has m1 and m2 defective alleles on opposite genes in both maternal and paternal chromosomes This image shows two E. coli cells, each infected with two T4 chromosomes. Mutations in the rII gene are indicated by the letter m and a subscript. Which cell(s) depict(s) a trans configuration? Multiple choice question. a) Both cells b) The right one c) The left one

a) both cells b/c trans configuration is when the 2 mutations are on different chromosomes aka both maternal and paternal chromosomes so in both cells, m1 mutation and m2 mutation are on two separate chromosomes even though they are on different positions or on different genes.....but on separate chromosomes nonetheless cis configuration would have been if the 2 mutations were both on maternal chromosome or both on paternal chromosome

Benzer predicted that crossing-over between homologous chromosomes carrying different mutations in the same gene should be able to generate a wild-type allele, even if very infrequently. He based this prediction on the idea that _____. Multiple choice question. a) genes are composed of separately mutable subunits b) mutations always change a gene in the same way c) each mutation in a gene is due to a change in a single nucleotide

a) genes are composed of separately mutable subunits

CH 8.1 When studying the rII gene in the T4 phage, Benzer needed to perform complementation tests to verify that rII— mutations are in the same gene. He did this by ______. Multiple choice question. a) infecting E. coli K(λ) cells with two types of T4 chromosomes, each carrying a different rII— mutation b) infecting E. coli K(λ) cells with two types of T4 chromosomes, both carrying the same rII—mutation c) infecting E. coli K(λ) cells with two types of T4 chromosomes, one carrying an rII— mutation and the other carrying the wild-type rII gene

a) infecting E. coli K(λ) cells with two types of T4 chromosomes, each carrying a different rII— mutation

In most organisms (for example, bacteria or humans), the rate of spontaneous mutations introduced during DNA replication is less than ____. Multiple choice question. a) once in 10^9 base pairs b) once in 10^6 base pairs c) once in 10^12 base pairs d) once in 10^3 base pairs

a) once in 10^9 base pairs

A tautomerization is a ____. Multiple choice question. a) temporary change in base structure b) base change caused by chemical agents c) temporary change in gene expression d) base change caused by ultraviolet light

a) temporary change in base structure

The sequence of bases in mRNA is determined by Multiple Choice a) the base sequence in DNA. b) the order of amino acids in the protein. c) the base sequence in tRNA. d) the base sequence in rRNA.

a) the base sequence in DNA.

ch 8.1 In Benzer's phage experiments, he was able to recognize the rII— mutants by ______. Multiple choice question. a) their inability to infect E.coli K(λ) b) the appearance of large plaques on E.coli K(λ) c) the viral coat morphology d) the loss of antibiotic resistance in infected E. coli cells

a) their inability to infect E.coli K(λ)

ch 8.1 Choose all of Benzer's conclusions based on the precise maps he constructed of mutations in the rIIA and rIIB genes of the T4 bacteriophage. Multiple select question. a) The nucleotide sequences of the rIIA and rIIB genes are separate and distinct. b) Mutations can result from a change of a single nucleotide pair in DNA. c) A gene is composed of a continuous linear sequence of nucleotide pairs within DNA. d) Not all mutations result in changes in the amino acid sequence of a protein. e) The nucleotide sequences of the rIIA and rIIB genes exhibit a small overlap.

a, b, c

A genetic screen for eye color mutants resulted in five fly strains with independent mutations: three with white eyes and two with orange eyes. The genomic locations of each of the five mutations has been identified. What results are possible? Check all that apply. Multiple select question. a) All mutations are in the same gene. b) The five mutations are in five different genes. c) The white mutations are in one gene, the orange mutations in another. d) The mutations could represent up to ten different genes.

a,b,c

ch 8.1 The lowest recombination frequency measured by Benzer between any pair of rII— mutants was 0.02 m.u., which corresponds to ____. Multiple choice question. a) about 20 base pairs b) about 113 base pairs c) about 2 base pairs d) about 6 base pairs

about 2 base pairs The lowest RF that he measured between any pair of rII mutants was 0.02 m.u., which would represent about 2 bp Benzer knew that the genetic distances between all mapped genes in the T4 genome add up to about 1500 m.u. He also knew that the T4 chromosome constitutes about 169,000 bp of DNA, so he could calculate that for bacteriophage T4, 1 m.u. corresponds to 169,000 bp / 1500 m.u = 113 bp

A region of DNA has six copies of a trinucleotide repeat. During one round of replication, the newly synthesized strand slips as shown in the diagram. If the loop is not repaired (cut out), how many repeats will be present in DNA if this newly synthesized strand is used as a template in the next round of replication?

answer is 8. Slipped strand always gains or loses 2 triplet bases so if a) slipped strand is newly synthesized strand than add 2 bases to original amount on template or region of DNA stated in problem b) slipped strand is template strand than subtract 2 bases to original amount on complementary strand or region of DNA stated in problem

Double-strand breaks are typically repaired by which of the following? Multiple select question. a) Methyl-directed mismatch repair b) Homologous recombination repair c) Nucleotide excision repair d) Nonhomologous end-joining e) Photoreactivation

b and d

When DNA is damaged by UV light and is not repaired, Multiple Choice a)DNA replication can proceed as normal but transcription is prevented. b) neither DNA replication nor transcription can occur and the organism will probably die. c) the damaged part will be excised and allow DNA replication to proceed. d) transcription can proceed as normal but replication is prevented.

b) neither DNA replication nor transcription can occur and the organism will probably die

Unstable trinucleotide repeats are repeated sequences of three bases ____. Multiple choice question. a) that are associated with various cancers b) that can increase or decrease in number generation after generation c) that can be used as templates to repair damaged DNA d) that can increase in number via reciprocal translocations

b) that can increase or decrease in number generation after generation

One reason DNA polymerase makes mistakes is because of the existence of ____________, alternate forms of bases that pair differently than the usual forms do. A second source of mistakes by DNA polymerase is ____________ which can occur when DNA polymerase is copying repetitive regions of DNA.

base tautomers slipped mispairing

Which of the following accurately describes a mechanism by which spontaneous heritable mutations can appear? Multiple choice question. a) All that is needed for a heritable mutation is an alteration in the sequence of DNA. b) In order for a heritable mutation to appear, DNA must be altered and the altered sequence must be replicated several times. c) In order for a heritable mutation to appear, DNA must be altered and replicated before it is repaired.

c)

What is our current estimate of the rate of spontaneous mutations in eukaryotic organisms? Multiple choice question. a) About 10-9 mutations per gene per gamete b) About 10-3 mutations per gene per gamete c) About 10-6 mutations per gene per gamete

c) About 10-6 mutations per gene per gamete

Consider the following change in a DNA sequence (for simplicity only one of the DNA strands is written): 5'-AATGTGGATG-3' to 5'-AATGTGCATG-3'. What type of mutation is this? Multiple choice question. a) Frameshift mutation b) Somatic mutation c) Base substitution d) Deletion mutation

c) Base substitution

Assume that a new low-calorie sweetener is developed. Before being approved for human consumption, the mutagenicity of the new molecule is determined with the Ames test. The results are shown. HIS -- bacteria + distilled water ---------> 3 His− bacteria + distilled water + rat liver enzymes --------> 2 His− bacteria + sweetener ---------> 4 His− bacteria + sweetener + rat liver enzymes -----------> 65 What conclusion is most consistent with these data? Multiple Choice a) The sweetener is not mutagenic. b) Rat liver enzymes are highly mutagenic. c) The sweetener is not mutagenic but can be converted into strong mutagens. d) The sweetener is mutagenic and can be converted into strong mutagens. e) The sweetener and its conversion products are equally mutagenic.

c) The sweetener is not mutagenic but can be converted into strong mutagens. sweetner produces 4 colonies which is not much different than colonies produced by the control groups but once added together with the rat liver enzymes, number of colonies shoots up signifying a mutagen

Hydroxylating agents mutate DNA by ______ a(n) ______ group to(from) cytosine, which allows it to pair with adenine. Multiple choice question. a) adding; -NH2 b) removing; -NH2 c) removing; -OH d) adding; -OH

d) adding; -OH

The proofreading function of DNA polymerase reduces the error rate from about one in a million base pairs to about one in a ________ base pairs. Multiple Choice a) thousand b) hundred thousand c) ten thousand d) hundred million e) ten million

d) hundred million

If two mutants complement each other, you can conclude that the mutations are ____. Multiple choice question. a) in the same gene b) on the same chromosome c) in nearby genes d) in separate genes

d) in separate genes

In his experiments with Drosophila, Muller exposed male flies to increasingly large doses of X-rays and mated them to females that had a Bar-marked Balancer X chromosome. Bar-eyed F1 females carrying a paternal X chromosome with a lethal mutation would _______. Multiple choice question. a) produce sons only with normal eyes b) produce only daughters c) produce only sons d) produce sons only with Bar eyes

d) produce sons only with Bar eyes

ch. 8.1 The utility of the deletion mapping approach, as used by Benzer, is to _______. Multiple choice question. a) map the most important regions of the gene b) remove regions of DNA that would interfere with further experiments c) reconstitute the functional gene d) quickly map point mutations to a region

d) quickly map point mutations to a region

ch 8.1 To be able to efficiently map a thousand mutations, Benzer took advantage of a technique that first localized each mutation to a region of the rII locus. He was able to do that by using phage strains that contain large _________ in the rII locus.

deletions