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1、GeneticCounselingandRiskAssessmentEthicalIssuesinMedicalGenetics Determiningrecurrencerisks Theprocessofgeneticcounseling Ethicalissuesinmedicalgenetics Outline TOMASTER WhatisgeneticcounselingRisksestimationbyuseofconditionalprobabilitywhenalternativegenotypesarepossibleMajorethicalpolicyinmedicalg
2、enetics Whatisgeneticcounseling Aprocessofcommunicationtoprovideinformationandsupporttofamiliesatriskforhaving orwhoalreadyhave memberswithbirthdefectsorgeneticdisease Incommondisorders givenbythefamilydoctor thepediatricianortheobstetrician RECENTLY byGeneticCounselor GeneticCounselor GC isahealthc
3、areprofessionalwithamaster sdegreeinhumangeneticsandcounseling ThistrainingenablesGCstodiscusstechnicalgeneticinformationinpractical usefulterms Whoprovidegeneticcounseling Commonindications PreviouschildwithgeneticdisorderFamilyhistoryofahereditaryconditionPrenataldiagnosisConsanguinityTeratogenexp
4、osureRepeatedpregnancylossorinfertilityNewlydiagnosedgeneticconditionbeforeundertakinggenetictestingandafterreceivingresultsAsfollow upforapositiveresult Geneticcounselingcasemanagement CollectionofinformationFamilyhistoryMedicalhistoryTestand oradditionalassessmentAssessmentPhysicalexaminationValid
5、ationorestablishmentofdiagnosis CounselingNatureandconsequenceofdisorderRecurrenceriskAvailabilityoffurtherorfuturetestingDecisionmakingReferraltootherspecialists healthagencies supportgroupsFollow upContinuingclinicalassessmentPsychosocialsupport Example MsWang 30yearoldfemale screened forDownsyndr
6、omeStep1 preassenssmentFamilyhistory anyfamilymembermaybeaffectedbythesimilarillness pedigreeMedicalhistory especiallyforthesickindividual MsWang sbrother wasbornnormal Assessment mentalretardationwassuspected moretestwillbeperformed Step2 counselingExplainMSSresultandDownsyndromeOptionsforfurtherdi
7、agnosisDiscussiononfamilyhistoryBrother scaseOptionstoclarifyingthesickness Example Test brother Geneticsdiseases Nogeneticcause Test MsWang carrier Notcarrier Test Fetus Discussion Fetuskaryotyping Explanation Example Determiningrecurrencerisks acentralconcerningeneticcounseling Riskestimationwheng
8、enotypesarefullyknownbyuseofMendel slaws AutosomaldominantWhatistheprobabilitythatindividual3willbeaffected 1 2 3 Aa aa AutosomalrecessiveWhatistheprobabilitythatindividual5willbeaffected Aa Aa X linkedrecessiveWhatistheprobabilitythatthewomanwillhaveanaffectedson Riskestimationbyuseconditionalproba
9、bilitywhenalternativegenotypesarepossible Bayesiananalysis Amethodthattakesadvantageofphenotypicinformationinapedigreetoassesstherelativeprobabilityoftwoormorealternativegenotypicpossibilitiesandconditiontheriskonthebasisofthatinformation Conditionalprobability HowtocalculateactualriskusingBayes the
10、orem PriorprobabilitythataFemaleinthepopulationisaCarrierofanX linkedlethaldisorder H thepopulationfrequencyoffemalecarriersAssume HisconstantfromgenerationtogenerationThemutationrateinanyonegamete anditisthesameinmalesandfemales Threewaysthatanyfemalecouldbeacarrier Amutantallelefromacarriermother
11、1 2HAnewlymutantalleleontheXfromhermother AnewlymutantalleleontheXfromherfather H 1 2 H H 4 ConditionalprobabilityinX linkedlethaldisorders A III 1isanewmutation B I 1isnotacarrier II 1mustbetheproductofamaternalorpaternalnewmutation C I 1andII 2arebothcarriers Priorprobabilities Conditionalprobabil
12、ities u IIIIII 12 12 12 IIIIII 2u 12 12 12 IIIIII 1 2 12 12 12 4u 1 2 1 2 TheriskthatII 1isacarrier 1 3 1 3 2 3TheriskthatIII 2isacarrier 2 3 1 2 1 3 BayesianCalculationforMothersofIsolatedCasesofX LinkedLethalDisorders Thepenetranceis70 Whatistheprobabilitythatindividual3willhaveanaffectedchild Dis
13、orderwithincompletepenetrance Theprobabilityis3 13 1 2 7 10 8 Individual3is30year old Whatistheprobabilitythatindividual3willbeaffected Disorderwithlateageatonset Theprobabilityis40 Inthispedigree whatistheprobabilitythatindividualSisaffected Shewillhaveanaffectedson 1 25 1 2 1 50 X linkedrecessiveW
14、hatistheprobabilitythatthewomanMwillhaveanaffectedson Shewillhaveanaffectedson 1 9 1 2 1 18 MajorEthicalandPolicyIssuesinMedicalGenetics GenetictestingPrivacyofgeneticinformationMisuseofgeneticinformationGeneticscreening Ethicalissuesingenetictesting Prenataltesting especiallyfornon diseasetraitsorsexTestingasymptomaticadultsforgenotypesthatpredispositiontolate onsetdiseasesTestingofasymptomaticchildrenforgenotypesthatpredispositiontoadult onsetdiseases 20y 19y 7y Thankyouandbestwishestoyouall
