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Updated SQ 12-15.docx

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University of Waterloo
BIOL 308
Dragana Miskovic

STUDY QUESTIONS LEC 1215 1 Distinguish between the terms DNA repair and recombination DNA repair re intrinsic mechanisms used by the body to repair faults in DNA and prevent mutationsDNA may not necessarily be repaired to its correctoriginal formRecombination is the exchange of genetic material between two DNA molecules causing rearrangement it increases variability Some forms of DNA repair incorporate recombination such as when a nick is encountered in DNA during replication2 List and briefly explain three major causes for mutation in DNA Errors from replication mistakes made during replication that were not detected and corrected by DNAPIIII proofreading mechanismsSpontaneous error depurination hydrolysis of Nglycosyl linkageabasic site in DNAloss in nucleotideC deaminationC U others incl Ahypoxanthine which pairs with C not T External factors External factors Radiation changes in temperature mutagens etcAlkylating chemicals adds alkyl group to DNAReactive oxygen species base pairs with A and C Highly mutagenicNonionizing radiation UV 260nm highly absorbed by bases Leads to thymine dimers that cause Xeroderma PigmentosumIonizing radiation X rays and gamma rays double strand breaksBase analogues 5 bromouracilT and replaces itIntercalating agents insert between stacked DNA bases May cause deletion or addition of bases and therefore frame shift3 Explain how errors in DNA replication can lead to mutationsFailure to repair DNA before the next round of replication will lead to permanent change in DNA mutation This is because the two strands will separate and the new strands formed will carry the complementary bases to the mutated bases and thus the mutation now doesnt need repair and becomes permanent4 Distinguish between the effects of mutations on the somatic and germ cells of multicellular organismA mutation in a somatic cell is not hereditary not passed vertically as somatic cells do not contribute to gametes however the mutation can still be detrimental and can cause cancersA mutation in the germ cells or the germ cell precursors can lead to hereditary diseases as the mutated DNA will form the original template used to make the DNA in the other cells and will therefore be passed on5 List the various types of DNA repair mechanism we have mentioned sevenExonuclease activity of polymeraseBase excision repairNucleotide excision repairNonhomologous end joint repairDirect reversal repairRecombination repairErrorprone repair translesion repair NHEJ
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