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1、最新医学遗传学17出生缺陷engv-药学医学精品资料1.GeneralOneofthemostcommonworriesforexpectantparentsisthatsomethingwillbewrongwiththeirbaby.However,mostbabiesarebornwithoutproblems,whilemostofthosewhoarecanhavetreatmentthatwillmakethemmuchbetter,orevenallowthemtoleadanormallife.T
2、hereisconsiderableregionalvariationintherateofdefectsseenatbirth.GlasgowandDublinhavetraditionallybeenblackspots,withratesover3percent,butthesefiguresarefalling.Thenumberofbabiesactuallybornwithdefectsisalsomarkedlyaffectedbytheavailabilityofprenatalscreening
3、,andtheavailabilityofvoluntaryterminationofpregnancyinthecaseofsevereabnormalities.2.FormsofBirthDefectsDefectsoflimbs,heartandspinalcordrepresentabouthalfofallabnormalities.Themostcommonkindsofdefectarethoseaffectingthelimbs(armsandlegs).Theseincludemissingo
4、rextrafingersortoes,deficienciesinlimblength,andabnormalitiesinpositioning,suchasclubfoot.Heartabnormalitiesrepresentthenextmostcommoncategoryofdefect.Commonheartdefectsinclude'holesintheheart'wherebloodcanpassfromonesideofthehearttotheother.Again,thesemaynot
5、allbedetectedatbirth.Thethirdmostcommonkindofdefectaffectsthespinalcord,suchasspinabifida.Otherdefectscommonlyobservedincludethoseaffectingtheface(suchascleftlipandpalate),problemswiththedevelopmentoftheintestinesandstomach,andproblemsaffectingthesexualorgans
6、.MajorchromosomalproblemssuchasDown'ssyndrome(Trisomy21)arefoundinabout0.15percentofbirths(aboutthreebabiesinevery2000).3.ThecauseofbirthdefectsA.GeneticsGeneticsplayaroleinsomebirthdefects.Onemissingorfaultygenecancauseabirthdefect.Inancienttimes,abnormaliti
7、eswereseenaswarningsorpunishmentsfromthegods.Evenquiterecently,itwasbelievedthatspecificeventsduringthepregnancy-suchasbeingfrightenedbyamouse-wouldleadtospecificdefectsinthebaby,egamouseshapedbirthmark.Suchfolkbeliefsstillpersistinplaces.However,mostdefectst
8、hatcanbetracedtoasinglecausehaveageneticorigin.Thisdoesnotnecessarilymeanthattheparentssufferfromthesamedefect.Itmaybethattheyarecarriersofthecondition,orthatthegeneticproblemoccurredfort
