Genetic disorders: Definition, development, and examples

asthma · heart disease · diabetes; certain cancers · schizophrenia · Alzheimer's disease · multiple sclerosis. Certain genetic mutations can increase the risk ... WhattoknowaboutgeneticdisordersMedicallyreviewedbyHarshilMatta,DO—WrittenbyAaronKandolaonSeptember14,2020DefinitionWhatisthehumangenome?DevelopmentSingleinheritanceMultifactorialinheritanceChromosomalabnormalitiesMitochondrialinheritanceSummaryAgeneticdisorderisaconditionthatoccursasaresultofamutationtoDNA.Thereareseveraldifferentgeneticdisorders.MostcellswithinthebodycontainthemoleculeDNA.Thismoleculeprovidesthecellwithinstructionsonhowtofunction.AchangeormutationwithintheDNAcancausethecelltofunctionabnormally.Thisarticleoutlineswhatgeneticdisordersare.Itdiscussesthedifferenttypes,themainsymptomsofeachtype,andhowtheydevelop.DefinitionShareonPinterestMutationsinDNAcanresultingeneticdisorders.GeneticdisordersareconditionsthatoccurasaresultofchangestoormutationsinDNAwithinthebody’scells.MostcellsinthebodycontainlongstrandsofDNAthatprovidethecellwithinstructions.EachDNAstrandistightlycoiledaroundaproteincalledahistone.Thiscoiledstructureiscalledachromosome.ChromosomescontainsmallsectionsofDNAcalledgenes.Thesegenesprovidethebodywithaspecificsetofinstructions.Eachhumancellnormallycontains23pairsofchromosomes,withoneofeachpairprovidedbyeachparent.Therefore,apersonhastwocopiesofeverygene.AchangeorfaultintheDNAcancauseageneticcondition.Sincegenespassfromparenttochild,thesedisordersmaybeheritable.However,noteveryonewithageneticconditionintheirfamilywillexperiencesymptomsofthedisorder.Geneticconditionscanaffectanygeneorchromosome.Thismeansthatthereareawiderangeofgeneticdisorders,eachcausingvarioussymptoms.Whatisthehumangenome?ThehumangenomereferstoallthegenesandDNAnecessarytobuildandmaintainahuman.TheHumanGenomeProject(HGP)wasaglobalresearchprojecttomapthehumangenome.Theprojectestablishedthesequenceofthehumangenomeandthefunctionofdifferentgenes.TheHGPestimatedtheretobearound20,000–25,000genesinthehumangenome.TheDNAinsidethesegenescontainfourchemicalbasesthatactasunitsofinformation.Theyare:adeninecytosineguaninethymineEachDNAmoleculecontainstwotwistedstrandsofDNA.PairsofchemicalbasesconnectoneDNAstrandtotheother,resemblingtherungsofaladder.Thebasepairsofchemicalsbetweeneachstrandalwayscombineinaspecificway.Forexample,adenineononeDNAstrandalwayspairswiththymineontheoppositeDNAstrand.TheorderofthechemicalbasepairsineachmoleculeofDNAaffectswhatinstructionstheDNAprovidestothebody.DNAsequencinginvolvesreadingtheorderofthesebasepairs.Sequencingthehumangenomewasanimportantstepinunderstandinghowgenescancausedisease.DevelopmentGeneticconditionstendtoruninfamilies.Parentspassgenesontotheirchildren,andsomeofthesegenesmaycontainthebasisofageneticdisorder.However,eachparentonlypassesdownhalfoftheirgenes.Theversionofeachgenethataparentpassesdownisknownasanallele.Iftwoallelesfromeachparentdiffer,thebodymayonlytakeinstructionsfromoneofthem.Theallelethatthecelltakesinstructionsfromisknownasthedominantallele.Theotherisknownastherecessiveallele.Somegeneticconditionsarecarriedbyadominantallele,whileothersarecarriedbyarecessiveallele.Generally,apersonwillonlyinheritaparticulargeneticdisorderiftheyhaveatleastonedominantalleleforthedisorderortworecessiveallelesforthedisorder.SingleinheritanceAsingleinheritance,ormonogenic,disorderisaconditionthatresultsfromafaultwithinasinglegene.Thesectionsbelowwilloutlinesomeexamplesofsingleinheritanceconditions.Huntington’sdiseaseHuntington’sdiseaseisadegenerativebraindisorderthatcauses:uncontrolledmovementsemotionaldisturbancescognitivedeclineHuntington’sdiseasedevelopsduetoamutationonadominantallelewithinchromosome4.Peoplewiththisallelewilleventuallydevelopthecondition.TreatmentThereiscurrentlynowaytostoporslowtheprogressionofHuntington’sdisease.However,certainmedicationsmayhelpapersonmanagetheirsymptoms.Theseincludemedicationstohelpcontrolinvoluntarymovementsandmedicationstotreatmoodshifts,irritability,anddepression.SicklecelldiseasesSicklecelldiseases(SCDs)areagroupofconditionsthataffectredbloodcells.SicklecellanemiaisatypeofSCDinwhichtheredbloodcellsthattransportoxygentothebody’stissuesaremisshapen.Theirunusualshapemeansthattheyarelessabletotransportoxygenandmorelikelytoclumptogether.Clumpsofthesebloodcellsmayblockabloodvessel,potentiallycausing:paininfectionsacutechestsyndromestrokeSCDsoccurasaresultofmutationsintheHBBgene.Thisgeneprovidesinstructionsfortheproductionofredbloodcells.SCDsarerecessive.Thismeansthatapersonwouldneedtoinherittwoallelescontainingthemutationinordertohavethedisorder.TreatmentTreatmentsforSCDsaimtopreventcomplicationsandprolonglife.Adoctormayprescribethemedicationhydroxyureatoincreasethesizeofredbloodcells,therebyincreasingtheamountofoxygeneachcellcantransport.MusculardystrophiesMusculardystrophiesareagroupofgeneticconditionsthatcausemuscledamageandweaknessovertime.TheyareduetomutationsontheDMDgene.MusculardystrophiesareX-linkeddisorders,meaningthattheyaffectageneontheXchromosome.Theseconditionsaremorecommoninmales.ThisisbecausemaleshaveoneXchromosomeandoneYchromosome,whereasfemaleshavetwoXchromosomes.Infemales,theunaffectedXchromosomecancounteracttheaffectedone,butinmales,thereisnotanotherXchromosometodothis.TreatmentThereiscurrentlynotreatmentavailabletostoporreversemusculardystrophies.Instead,treatmentaimstopreventcomplicationsandimproveaperson’squalityoflife.Examplesofsuchtreatmentsinclude:physicaltherapy,tohelpmaintainmusclestrengthandflexibilityrespiratorytherapy,tohelpmaintainthestrengthoftherespiratorymusclesspeechtherapy,forpeopleinwhomaweaknessofthethroatorfacialmusclesaffectsspeechoccupationaltherapy,tohelpapersonuseassistivedevicessuchaswheelchairsoneormoreofthefollowingmedications,tohelpsloworcontrolsymptoms:glucocorticoids,toincreasemusclestrengthandslowtheprogressionofmuscleweaknessimmunosuppressants,whichmayhelpdelaydamagetomusclecellsanticonvulsants,tohelpcontrolmusclespasmsandseizuresantibiotics,totreatrespiratoryinfectionsMultifactorialinheritanceMultifactorialinheritancedisorders(MIDs)areconditionsthatdevelopduetoacombinationofgeneticfactorsandenvironmentalorlifestylefactors.Someofthesenon-geneticfactorsmayinclude:smokingdrinkingalcoholeatinganunhealthfuldietnotgettingenoughsleeplivinginanareathathashighlevelsofairpollutionSomeconditionsthatmayfallintothecategoryofMIDsinclude:asthmaheartdiseasediabetescertaincancersschizophreniaAlzheimer’sdiseasemultiplesclerosisCertaingeneticmutationscanincreasetheriskoftheseconditions.However,thereisnoclearpatternofinheritance.ChromosomalabnormalitiesChromosomalabnormalitiesareproblemsthataffectachromosome.Chromosomalabnormalitiescaninvolve:havingamissingchromosomehavinganextrachromosomehavingachromosomethathassomekindofstructuralabnormalityChromosomalabnormalitiesusuallyoccurwhenthereisanerrorasacellisdividing.Theseerrorsusuallyoccurwithintheeggorsperm,buttheycanalsohappenafterconception.Itispossibletoinheritachromosomalabnormalityfromaparent.However,somedevelopwithinapersonforthefirsttime.Thesectionsbelowwilloutlinesomeexamplesofchromosomalabnormalities.DownsyndromeDownsyndromeisatypeofchromosomalabnormalitythataffectsintellectualandphysicaldevelopment.Downsyndromeoccurswhenapersonreceivesanextracopyofchromosome21.Thismeansthateachcellwithinthebodycontainsthreecopiesofchromosome21insteadoftheusualtwocopies.TreatmentsDownsyndromeisalifelongcondition.However,varioustypesoftherapycanhelpwithaperson’sintellectualandphysicaldevelopment.Examplesinclude:receivingextrahelporattentionatschoolspeechtherapyphysicaltherapyoccupationaltherapyWolf-HirschhornsyndromeWolf-Hirschhornsyndromeisachromosomalabnormalitythatcanaffecttheentirebody.Themajorfeaturesofthisconditioninclude:delayedgrowthanddevelopmentreducedmuscletoneintellectualdisabilitiesseizuresWolf-Hirschhornsyndromedevelopsduetoadeletionofasectionofchromosome4.Mostcasesoccurforthefirsttimewithinthepersonwhohasthedisorder.However,itisalsopossibleforapersontoinherittheconditionfromaparentwhohasthechromosomalabnormality.TreatmentThereiscurrentlynocureforWolf-Hirschhornsyndrome.However,thefollowingtreatmentsmayhelpapersonmanagetheirsymptomsandimprovetheirqualityoflife:physicaloroccupationaltherapycounselingdrugsthatcanhelpwithspecificsymptoms,suchasseizuresMitochondrialinheritanceMitochondriaarebiologicalstructuresthatexistinsidethebody’scells.Theygeneratemostoftheenergythatthecellsneedtocarryouttheirbiochemicalreactions.MitochondrialdisordersareagroupofgeneticconditionsthataffectDNAwithinthemitochondriathemselves.TheseDNAmutationsresultinthemitochondriafailingtoproduceenoughenergytosustainthebody’scells.Mitochondrialdisorderscanaffectanyorganorpartofthebody.Thesymptomsapersonexperienceswilldependonthepartofthebodythedisorderaffects.Somepossiblesymptomsofmitochondrialdisordersinclude:poorgrowthmuscleweaknesslossofmusclecoordinationvisualproblemshearingproblemsseizuresdevelopmentaldelaysintellectualdisabilitiesautismspectrumdisorderdiabetesheart,liver,orkidneydiseaserespiratorydisordersMutationsinmitochondrialDNAareinheritedmaternally.Thismeansthatonlyamothercanpassdownmitochondrialdisorders.TreatmentThereiscurrentlynocureorhighlyeffectivetreatmentformitochondrialdisorders.However,thefollowingtreatmentsmayhelpapersonmanagethem:nutritionalmanagementvitaminsupplementsaminoacidsupplementsmedicationsthathelptreatspecificissues,suchasmuscleweaknessorseizuresSummaryGeneticdisordersoccurasaresultofamutationtoDNA.Thismutationmayaffectwholechromosomesorthespecificgeneswithinchromosomes.DNAmutationsmayalsohappenwithintheDNAofmitochondria,whichpoweraperson’scells.Mostgeneticconditionsareheritable,butsomecanoccurforthefirsttimewithinthepersonwhoexperiencesthedisorder.Geneticdisordersarelifelongconditions.Forthisreason,treatmentstendtofocusonhelpingapersonmanagethesymptoms,preventingcomplications,andimprovingqualityoflife.Insomecases,theremaybemedicationsavailabletohelpslowtheprogressionofaparticulardisease.LastmedicallyreviewedonSeptember14,2020GeneticsHuntington'sDiseaseMuscularDystrophy/ALSMedicallyreviewedbyHarshilMatta,DO—WrittenbyAaronKandolaonSeptember14,2020LatestnewsGhrelin:AllaboutthehungerhormoneMuscle-strengtheningexercisesmaylowerriskofdeathVitaminD3,butnotD2,linkedtoimprovedimmu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