2014 Pearson Education, Inc.The Mutability and Repair of DNA课后作业2014-9-29 2014 Pearson Education, Inc.1. Which one of the following is an example ofa mutation?A.oxidation of guanine to produce7,8-dihydro-8-oxoguanine or oxoGB.formation of a thymine dimerC.alkylation of guanine to produceO6-methylguanineD.deamination of cytosine, followed by around of DNA replication. 2014 Pearson Education, Inc.2. What pathway removes uracil present in DNA? A.base excision repairB.nucleotide excision repairC.nonhomologous end joiningD.translesion synthesis 2014 Pearson Education, Inc.3. Dam methylase plays a role in mismatch repair in E. coli.Which of the following statements is true if Dam methylaseis absent?A.There would be no effect on mismatch repair.B.The newly synthesized daughter strand containingthe incorrect base and the parental strand will bothbe unmethylated and, therefore, either strand canserve as the template strand for mismatch repair.C.All DNA would remain methylated and therefore either strand can serve as the template strand for mismatchrepair.D.Only the parent strand would be methylated and, therefore, only the parental strand can serve as the template strandfor mismatch repair. 2014 Pearson Education, Inc.4. Base excision repair (BER) differs from nucleotide excision repair (NER) in which of the following ways?A.BER recognizes helix distortions, while NERrecognizes specific base damage.B.NER recognizes helix distortions, while BERrecognizes specific base damage.C.BER involves a DNA synthesis step, while NER does not.D.NER involves the removal and replacementof DNA containing altered bases, while BERdoes not. 2014 Pearson Education, Inc.5. Which one of the following statements is true regarding transcription-coupled repair? A.Transcription-coupled repair corrects damagein mRNA.B.Transcription-coupled repair occurs onlyduring S phase of the cell cycle.C.Transcription-coupled repair involves all themajor nucleotide excision repair proteins, aswell as RNA polymerase.D.Transcription-coupled repair occurs inresponse to the stalling of a ribosome. 2014 Pearson Education, Inc.6. Translesion DNA synthesis accomplishes which of the following?A.repairs DNA mutationsB.removes damaged DNAC.allows DNA replication to proceed aroundDNA lesions that stall the replication forkD.stalls the replication fork 2014 Pearson Education, Inc.7. Methylation and subsequent deamination of cytosine produces what type of mutation after one round of DNA replication?A.C-to-T transversionB.C-to-T transitionC.G-to-A transitionD.C-to-A transversion 2014 Pearson Education, Inc.Question 8. DNA polymerase mistakenly inserts a C across from a T during replication. Assuming that proofreading and mismatch repair do not correct the mismatch, is the resulting mutation a transition or transversion after the next round of replication? Explain your choice.Question 9. Explain why the deamination of 5-methylcytosine leads to hot spots for spontaneous mutations more than the deamination of cytosine in DNA does.Question 10. The following terms describe the general steps of a DNA repair pathway. Place the steps in the correct order. Name the protein(s) that complete each of the steps in E. coli for the mismatch repair, base excision repair, and nucleotide excision repair pathways.Ligation, DNA synthesis, Recognition, Excision 2014 Pearson Education, Inc.Question 11. Exposure of DNA to the chemotherapy drug, cisplatin, causes the formation of intrastrand cross-links between two adjacent guanines in DNA. Explain why the instrastrand cross-link between two adjacent guanines is a better candidate for nucleotide excision repair rather than for base excision repair.Question 12. Explain the difference between DNA repair and DNA damage tolerance.Question 13. Given a loss-of-function mutant for dam (the gene encoding the Dam methylase) in E. coli, predict the phenotype one would observe with respect to spontaneous mutagenesis. Briefly explain your answer.