Chapter 15 Gene Mutation, DNA Repair, and Transposition1) Mutations that arise in nature, from no particular artificial agent, are called ________.A) natural mutationsB) induced mutationsC) spontaneous mutationsD) chromosomal aberrationsE) cosmic mutationsAnswer: CSection: 15.1, 15.22) Nutritional mutations can be defined as ________.A) those mutations that do not allow an organism to grow on minimal medium but do allow growth on complete mediumB) those mutations that change the composition of the mediumC) those mutations belonging to the group called prototrophsD) those mutations caused by site-specific mutagenesisE) all strains that are not auxotrophicAnswer: ASection: 15.13) Conditional mutations are more likely to result from a mutation caused by which of the following alterations to the coding region of a gene?A) four bases added within a short region of a geneB) base additionC) X-raysD) deletionE) tautomeric shiftAnswer: ESection: 5.14) Two formal terms used to describe categories of mutational nucleotide substitutions in DNA are ________.A) base analogs and frameshiftB) error prone and spontaneousC) transversions and transitionsD) euchromatic and heterochromaticE) sense and antisenseAnswer: CSection: 15.11Copyright © 2012 Pearson Education, Inc.5) Which of the following name two mutagens that would be classified as base analogs?A) acridine orange and proflavinB) ethylmethane sulfonate and ethylmethylketone peroxideC) ultraviolet light and cosmic radiationD) 5-bromouracil and 2-aminopurineE) hydroxyurea and peroxidaseAnswer: DSection: 15.36) A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be which of the following?A) base analogB) transversionC) transitionD) frameshiftE) recombinantAnswer: DSection: 15.17) Ultraviolet light causes pyrimidine dimers to form in DNA. Some individuals are genetically incapable of repairing some dimers at "normal" rates. Such individuals are likely to suffer from ________.A) xeroderma pigmentosumB) SCIDC) phenylketonuriaD) muscular dystrophyE) Huntington diseaseAnswer: ASection: 15.58) Transposons, or jumping genes, are DNA elements that move within the genome. In which organismic groups are transposons found?A) bacteriaB) eukaryotesC) mammalsD) ancient bacteriaE) all organismic groupsAnswer: ESection: 15.82Copyright © 2012 Pearson Education, Inc.9) All insertion sequences (IS elements) contain two features that are essential for their movement. What are these two elements?A) transposase and inverted terminal repeatsB) integrase and pseudogenesC) integrase and oncogenesD) proto-oncogenes and oncogenesE) transposase and oncogenesAnswer: ASection: 15.810) Some bacterial transposons, known as Tn elements, are larger than insertion sequences (IS elements) and contain protein-coding genes that have human health significance. What might such a bacterial transposon contain?A) drug resistanceB) oncogeneC) pseudogeneD) proto-oncogeneE) dissociation elementAnswer: ASection: 15.811) Barbara McClintock discovered mobile elements in corn by analyzing the genetic behavior of two elements, Ds and Ac. The interplay between these two elements has become one of the most interesting stories of discovery in the field of genetics. How do Ds and Ac interact?A) Ds causes a deletion next to the insertion site of Ac.B) Ac causes a deletion next to the insertion site of Ds.C) While Ds moves only if Ac is present in the genome, Ac is capable of autonomous movement.D) The movement of Ac is dependent on two forms of Ds.E) Both elements can move only within chromosome 9.Answer: CSection: 15.812) DNA may be damaged from the by-products of normal cellular aerobic respiration. Name three of these electrophilic oxidants that are generally classified as reactive oxidants.Answer: superoxides(O2-), hydroxyl radicals (·OH), and hydrogen peroxide (H2O2)Section: 15.213) Describe the mutagenic action of the following two mutagens:5-bromouracil and ultraviolet light.Answer: The mutagen 5-bromouracil is an analog of thymine, which anomalously pairs with guanine. Ultraviolet light causes thymine dimers.Section: 15.33Copyright © 2012 Pearson Education, Inc.14) Some mutagens cause genetic changes that can be "corrected" by reexposing cells to the same mutagen. Other mutagens do not behave in this way. Provide one example of each of these two types of agents and describe the mutational changes caused in DNA. Explain why some mutagens behave in one way, while others do not.Answer: Mutagens that cause base substitutions are "corrected" by mutagens of the same class (nitrous acid, 2-aminopurine, and 5-bromouracil). Frameshift mutations are "corrected" by the same class of frameshift mutagens, but not by mutagens that cause base substitutions. X-rays cause major structural changes in chromosomes (deletions, translocations, etc.) and are not "corrected" by any mutagen, including X-rays.Section: 15.1, 15.2, 15.315) It has been found that a particular "+ -" combination of frameshift mutations in gene X gives a wild-type phenotype, whereas a "- +" combination gives a mutant phenotype, even though the sites of insertion/deletion are the same. How might these results be explained?Answer: A frameshift in the "+ -" direction may have introduced a nonsense triplet, which was not introduced, by chance, by the opposite "- +" combination.Section: 15.1, 15.3, 15.416) Mutations may exert a variety of effects on living systems. List at least three categories of mutations based on their biological effects.Answer: morphological mutations, nutritional or biochemical mutations, behavioral mutations, regulatory mutations, lethal mutations, conditional mutationsSection: 15.117) Under certain conditions, the rate of mutation of a particular gene may be determined in humans. Which four properties of the mutation would favor the most direct determination of mutation rate in humans?Answer: dominant, fully expressed, 100% penetrant, single locusSection: 15.418) In a survey of 240,000 human births, six achondroplastic births were recorded to parents whowere unaffected. Given that this form of dwarfism is caused by a fully penetrant, dominant, autosomal gene, what is the mutation rate?Answer: 6/(4.8 × 105)Section: 15.419) Three human disorders—fragile-X syndrome, myotonic dystrophy, and Huntington disease—are conceptually linked by a common mode of molecular upset. Describe the phenomena that link these disorders.Answer: