医学遗传学 04基因突变的分子机制eng v.ppt

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1、Medical Genetics医学遗传学 04基因突变的分子机制eng v Still waters run deep.流静水深流静水深,人静心深人静心深 Where there is life,there is hope。有生命必有希望。有生命必有希望Medical Genetics1.GenescanbemutatedinmanywaysThemostcommongenechangeinvolvesasinglebasemismatch-amisspelling-placingthewrongbaseintheDNA.Atothertimes,asinglebasemaybedroppe

2、doradded.AndsometimeslargepiecesofDNAaremistakenlyrepeatedordeleted.Medical GeneticsMedical GeneticsWhenagenecontainsamutation,theproteinencodedbythatgeneislikelytobeabnormal.Medical GeneticsMedical GeneticsMedical Genetics2.SomaticversusgermlinemutationsGenemutationscanbeeitherinheritedfromaparento

3、racquired.Medical GeneticsMedical GeneticsHereditarymutationsarecarriedintheDNAofthereproductivecells.Whenreproductivecellscontainingmutationscombinetoproduceoffspring,themutationwillbeinalloftheoffspringsbodycells.Medical GeneticsThefactthateverycellcontainsthegenechangemakesitpossibletousecheekcel

4、lsorabloodsampleforgenetesting.Medical GeneticsMedical GeneticsAcquiredmutationsarechangesinDNAthatdevelopthroughoutapersonslifetime.Medical GeneticsAlthoughmistakesoccurinDNAallthetime,especiallyduringcelldivision,acellhastheremarkableabilitytofixthem.ButifDNArepairmechanismsfail,mutationscanbepass

5、edalongtofuturecopiesofthealteredcell.Medical GeneticsMedical Genetics3.Typesofmutationeffects(1)Morphologicalmutationsgiverisetoalteredforms.Medical GeneticsMedical GeneticsMedical Genetics(2)Lethalmutationsresultinnonviableorganisms.Medical Genetics(3)Conditionalmutationsgivesamutantphenotypeunder

6、restrictiveconditions(environmental)andcausesawildtypephenotypeunderpermissiveconditions.Medical Genetics(4)Biochemicalmutationsresultintheinabilitytocarryoutaspecificbiochemicalpathway(inbornerrorsofmetabolism).Medical Genetics(5)Loss-of-function(null)mutations(lof)resultinnogenefunctionareusuallyr

7、ecessivealthoughsomehaploinsufficientdominantlofmutationsexist.Medical GeneticsMedical GeneticsAcommonlofmutationisthepartialloss-of-functionorleakymutation.Medical GeneticsMedical Genetics(6)Gain-of-functionmutation(gof)resultinalteredgenefunctionthatactasadominantalleleandproducesanovelphenotype.Medical Genetics