《出生前基因型》PPT课件

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1、PrenatalgenotypingusingRFLPThedifferencesinRFLPpatternsareusedtodiagnosegeneticdisordersprenatallyandcanalsodeterminethegenotypeofparentsandotherfamilymemberswhomaybeheterozygouscarriers.ForprenataldiagnosisfetalcellsareobtainedbyamniocentesisThetoolsneededtoperformtheseDNAdia

2、gnosesarefirstweneedarestrictionenzymethatwillcutDNAinamannerthatisinformativeforthediseaseinquestion,andsecondweneedanucleicacidprobethatwilldetectthatregion1kb4kbsampleA:probexxxxxxxxxxSampleB:xxxxxxxxxxxThetwoDNAsamplesarecutwiththeappropriateenzymeandarehybridizedwiththeco

3、rrectprobe.Theprobehybridizedtothe1and4kbfragmentsinsampleAandthe5kbfragmentinsampleB.ThisisanexamplewherearestrictionsitehasbeengainedinsampleA(orlostinsampleB)bymutation.SampleASampleB--------------------------5.0kb___4.0kb___1.0kb___---------------------------GenotypeDeterm

4、inationusingRFLP'sandaGeneProbeADNAprobethathybridizestothe5'endofthehumanbetaglobingene(showninblueonthediagrambelow)wasusedtoidentifyRFLPpiecesfrommembersofafamilyinwhichsickle-cellhemoglobin(HbS)wassegregating.ThenormalHBallele(HbA)iscutatthreeplacesbyaparticularrestriction

5、enzyme(positionsshownwithredarrows).TheHbSmutationdestroystheinternalrestrictionsitesotheHbSgeneiscutinonlytwoplaces.Thus,theprobehybridizestoa1.15kbDNAfragmentfromHbADNAandhybridizestoa1.35kbfragmentfromHbSDNA.LinkedDNAmarkersAlloftheDNA(RFLPorPCR)markersthatwehavediscussedso

6、farhavebeentargetedtoaspecificgene.Formanyimportanttraits,theactualgeneofinterestisnotknown.Therefore,probingforthepresenceofthenormalormutatedalleleisnotpossible.Insteadtheproberecognizesasequencethatisclosetotheactualgeneofinterest.BoththephenotypeandtheRFLPmarkerisfollowedi

7、nthegenerations.RecombinationfrequenciescanbeestimatedandthedistancebetweenthemarkerandthegeneofinterestcanbedeterminedMarker1Marker21cM5cMGeneMarker1GeneMarker2

8、___________!_________!!There’sonly1%chancethatthelinkageisbroken,withmarker1.DNAsequencing-Isthedeterminationofthep

9、recisesequenceofnucleotidesinasampleofDNA.Themostpopularmetho