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Hoe beïnvloed die ouderdom van 'n ouer die kanse op voorkoms van sekere geneties oordraagbare siektes?

Hoe beïnvloed die ouderdom van 'n ouer die kanse op voorkoms van sekere geneties oordraagbare siektes?


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Het geneties oordraagbare ouderdomsverwante siektes (soos hipertensie, artritis ens.) die waarskynlikheid om op 'n vroeër (jonger) ouderdom by die nageslag te voorkom as hulle op 'n later ouderdom by hul ouer(s) gebore word?


In sommige studies het hulle óf positiewe óf negatiewe assosiasie tussen moeder- of vaderlike ouderdom (die ouderdom van moeder of vader ten tyde van aflewering) en vroeëre ontwikkeling van geneties aangelê siektes, soos diabetes tipe 1 en sekere kankers, by nageslag waargeneem.

Diabetes tipe 1

Moederouderdom en diabetes in die kinderjare (BMJ, 2010):

… die risiko van kinderdiabetes [tipe 1] verhoog met moederlike ouderdom: 5% vir elke vyfjarige ouderdom… die hoofverduidelikings is dat biologiese programmering van die kind op een of ander manier beïnvloed word deur die ouderdom van die moeder, of dalk die vader …

Kanker

Ouerlike ouderdom en risiko van sporadiese en familiële kanker by nageslag: implikasies vir kiemselmutagenese (Epidemiology, 1999)

Ons het die landwye Sweedse Gesinskankerdatabasis gebruik om die effek van ouerlike ouderdom op kanker by nageslag op die ouderdom van 15-53 jaar te ontleed ... Moederlike ouderdom was geassosieer met sporadiese melanoom en leukemie, wat 'n oormaat van 30% veroorsaak as moeders ouer as 40 jaar was teenoor minder as 20 jaar oud. 'n Marginale effek van ongeveer 10% van beide moederlike en vaderlike ouderdom is waargeneem vir sporadiese borskanker.

Vaderlike ouderdom het die RR van sporadiese senuweestelselkanker met ongeveer 15% verhoog. Ophoping van chromosomale afwykings en mutasies tydens die rypwording van kiemselle kan 'n meganisme vir hierdie bevindings wees. In familiale kankers van kolon, melanoom en skildklier het hoër ouderdom 'n oënskynlike beskermende effek getoon, wat ook opgemerk is vir sporadiese servikale kanker en melanoom.

Rumatoïede artritis

Ouderdomme van aanvang wat dui op genetiese afwagting in rumatoïede artritis multi-geval sibships kan verklaar word deur waarnemingsvooroordeel (Rheumatology, 2007)

Daar was geen beduidende korrelasie tussen die ouderdom van RA aanvang en die moederlike of vaderlike ouderdom van bevrugting nie.

Kardiovaskulêre siekte

In een studie het hulle geen beduidende verband tussen moederlike ouderdom en bloeddruk by kinders gevind nie. Daar blyk geen studies te wees oor die effek van moeder/vader ouderdom op vroeë-aanvang hartsiekte.

Aan die ander kant het die nageslag 'n groter risiko om vroeg 'n kardiovaskulêre siekte te ontwikkel as hul ouers dit vroeg gehad het (PLoS One, 2016).


In 'n ander studie het hulle waargeneem dat ouderdomme van die moeder <25 en >45 geassosieer word met verhoogde broosheidsindeks: 'n som van 8 toestande (kanker, longsiekte, geestesgesondheidsprobleme, diabetes, hartsiektes, beroerte, bloeddruk en artritis)

Moederouderdom en Nageslag Volwasse Gesondheid: Bewyse uit die Gesondheid- en Aftredestudie (Demografie, 2012)

Samevattend, naas 'n paar ooglopende verwarrs, word slegs moederlike ouderdom onder 25 en bo 45 met negatiewe gesondheidsuitkomste van die nageslag geassosieer. (sien Fig 1 en Tabel 2)

Die meganismes wat vermoedelik verantwoordelik is vir die jong moeder-ouderdom-nageslag-gesondheidsskakel hou verband met die fisiologiese onvolwassenheid en sosiodemografiese nadeel wat dikwels jong ouerskap vergesel ... Aan die ander kant word die negatiewe assosiasie tussen gevorderde moederouderdom en volwasse gesondheid vermoedelik gedryf. deur die fisiologiese reproduktiewe veroudering van die moeder.

In hierdie studie het hulle nie nagegaan vir die ouderdom van aanvang van siektes by nageslag, egter.


Wat beteken dit om 'n genetiese aanleg vir 'n siekte te hê?

'n Genetiese aanleg (soms ook genoem genetiese vatbaarheid) is 'n verhoogde waarskynlikheid om 'n spesifieke siekte te ontwikkel gebaseer op 'n persoon se genetiese samestelling. 'n Genetiese aanleg spruit uit spesifieke genetiese variasies wat dikwels van 'n ouer geërf word. Hierdie genetiese veranderinge dra by tot die ontwikkeling van 'n siekte, maar veroorsaak dit nie direk nie. Sommige mense met 'n predisponerende genetiese variasie sal nooit die siekte kry nie, terwyl ander sal, selfs binne dieselfde familie.

Genetiese variasies kan groot of klein uitwerkings hê op die waarskynlikheid om 'n spesifieke siekte te ontwikkel. Byvoorbeeld, sekere variante (ook genoem mutasies) in die BRCA1 of BRCA2 gene verhoog 'n persoon se risiko om borskanker en eierstokkanker te ontwikkel aansienlik. Besondere variasies in ander gene, soos BARD1 en BRIP1, verhoog ook die risiko van borskanker, maar die bydrae van hierdie genetiese veranderinge tot 'n persoon se algehele risiko blyk baie kleiner te wees.

Huidige navorsing is gefokus op die identifisering van genetiese veranderinge wat 'n klein effek op siekterisiko het, maar wat algemeen in die algemene bevolking voorkom. Alhoewel elkeen van hierdie variasies slegs 'n persoon se risiko effens verhoog, kan veranderinge in verskeie verskillende gene kombineer om die siekterisiko aansienlik te verhoog. Veranderinge in baie gene, elk met 'n klein effek, kan onderliggend wees aan vatbaarheid vir baie algemene siektes, insluitend kanker, vetsug, diabetes, hartsiektes en geestesongesteldheid. Navorsers werk daaraan om 'n individu se beraamde risiko vir die ontwikkeling van 'n algemene siekte te bereken, gebaseer op die kombinasie van variante in baie gene oor hul genoom. Hierdie maatstaf, bekend as die poligeniese risikotelling, sal na verwagting help om gesondheidsorgbesluite in die toekoms te rig.

By mense met 'n genetiese aanleg, kan die risiko van siekte afhang van verskeie faktore bykomend tot 'n geïdentifiseerde genetiese verandering. Dit sluit in ander genetiese faktore (soms genoem modifiseerders) sowel as lewenstyl- en omgewingsfaktore. Siektes wat deur 'n kombinasie van faktore veroorsaak word, word as multifaktoriaal beskryf. Alhoewel 'n persoon se genetiese samestelling nie verander kan word nie, kan sommige lewenstyl- en omgewingsveranderinge (soos meer gereelde siektesiftings en die handhawing van 'n gesonde gewig) die siekterisiko by mense met 'n genetiese aanleg verminder.


Alles oor genetika

Wat weet jy van jou stamboom? Het enige van jou familielede gesondheidsprobleme gehad wat geneig is om in gesinne te voorkom? Watter van hierdie probleme het jou ouers of grootouers geraak? Watter een raak jou of jou broers of susters nou? Watter probleme kan jy aan jou kinders oordra?

Danksy vooruitgang in mediese navorsing het dokters nou die gereedskap om baie te verstaan ​​oor hoe sekere siektes, of verhoogde risiko's vir sekere siektes, van geslag tot geslag oorgaan. Hier is 'n paar basiese beginsels oor genetika.

Gene en Chromosome

Elkeen van ons het 'n unieke stel chemiese bloudrukke wat beïnvloed hoe ons liggaam lyk en funksioneer. Hierdie bloudrukke is vervat in ons DNA (deoksiribonukleïensuur), lang, spiraalvormige molekules wat in elke sel voorkom. DNS dra die kodes vir genetiese inligting en is gemaak van gekoppelde stukke (of subeenhede) wat nukleotiede genoem word. Elke nukleotied bevat 'n fosfaatmolekule, 'n suikermolekule (deoksiribose) en een van vier sogenaamde "koderende" molekules wat basisse genoem word (adenien, guanien, sitosien of timidien). Die volgorde (of volgorde) van hierdie vier basisse bepaal elke genetiese kode.

Die DNA-segmente wat die instruksies bevat vir die maak van spesifieke liggaamsproteïene, word genoem gene. Wetenskaplikes glo dat menslike DNA ongeveer 25 000 proteïenkoderende gene dra. Elke geen kan beskou word as 'n "resep" wat jy in kookboek sal vind. Sommige is resepte om fisiese kenmerke te skep, soos bruin oë of krulhare. Ander is resepte om die liggaam te vertel hoe om belangrike chemikalieë genaamd ensieme te produseer (wat help om die chemiese reaksies in die liggaam te beheer).

Langs die segmente van ons DNA is gene netjies verpak binne strukture genoem chromosome. Elke menslike sel bevat 46 chromosome, gerangskik as 23 pare (genoem outosome), met een lid van elke paar wat van elke ouer geërf is ten tyde van bevrugting. Na bevrugting (wanneer 'n spermsel en 'n eiersel bymekaar kom om 'n baba te maak), dupliseer die chromosome keer op keer om dieselfde genetiese inligting aan elke nuwe sel in die ontwikkelende kind deur te gee. Twee-en-twintig outosome is dieselfde by mans en wyfies. Daarbenewens het wyfies twee X-chromosome en mans het een X- en een Y-chromosoom. Die X en die Y staan ​​bekend as geslagschromosome.

Menslike chromosome is groot genoeg om met 'n hoëkragmikroskoop gesien te word, en die 23 pare kan geïdentifiseer word volgens verskille in hul grootte, vorm en die manier waarop hulle spesiale laboratoriumkleurstowwe optel.

Genetiese probleme

Foute in die genetiese kode of "geenresep" kan op verskeie maniere gebeur. Soms ontbreek inligting in die kode, ander kere het kodes te veel inligting, of het inligting wat in die verkeerde volgorde is.

Hierdie foute kan groot wees (byvoorbeeld, as 'n resep baie bestanddele &mdash of almal ontbreek) of klein (as net een bestanddeel ontbreek). Maar ongeag of die fout groot of klein is, kan die uitkoms beduidend wees en veroorsaak dat 'n persoon 'n gestremdheid het of 'n risiko loop om 'n verkorte lewensduur te hê.

Abnormale getalle chromosome

Wanneer 'n fout plaasvind terwyl 'n sel besig is om te deel, kan dit 'n fout veroorsaak in die aantal chromosome wat 'n persoon het. Die ontwikkelende embrio groei dan uit selle wat óf te veel chromosome het óf nie genoeg nie.

In trisomiedaar is byvoorbeeld drie kopieë van een spesifieke chromosoom in plaas van die normale twee (een van elke ouer). Trisomie 21 (Down-sindroom), trisomie 18 (Edwards-sindroom) en trisomie 13 (Patau-sindroom) is voorbeelde van hierdie tipe genetiese probleem.

Trisomie 18 affekteer 1 uit elke 7 500 geboortes. Kinders met hierdie sindroom het 'n lae geboortegewig en 'n klein kop, mond en kakebeen. Hul hande vorm tipies gebalde vuiste met vingers wat oorvleuel. Hulle kan ook geboortedefekte hê wat die heupe en voete, hart- en nierprobleme en intellektuele gestremdheid behels. Slegs sowat 5% van hierdie kinders sal na verwagting langer as 1 jaar leef.

Trisomie 13 affekteer 1 uit elke 15 000 tot 25 000 geboortes. Kinders met hierdie toestand het dikwels gesplete lip en verhemelte, ekstra vingers of tone, voetafwykings en baie verskillende strukturele abnormaliteite van die skedel en gesig. Hierdie toestand kan ook geboortedefekte van die ribbes, hart, abdominale organe en geslagsorgane veroorsaak. Langtermyn-oorlewing is onwaarskynlik, maar moontlik.

In monosomie, 'n ander vorm van numeriese fout, een lid van 'n chromosoompaar ontbreek. Daar is dus te min chromosome eerder as te veel. 'n Baba met 'n vermiste outosoom het min kans op oorlewing. 'n Baba met 'n ontbrekende geslagschromosoom kan egter in sekere gevalle oorleef. Byvoorbeeld, meisies met Turner-sindroom &mdash wat met net een X-chromosoom &mdash gebore word, kan normale, produktiewe lewens lei solank hulle mediese sorg ontvang vir enige gesondheidsprobleme wat met hul toestand verband hou.

Skrapings, translokasies en inversies

Soms is dit nie die aantal chromosome wat die probleem is nie, maar dat die chromosome iets fout het met hulle, soos 'n ekstra of ontbrekende deel. Wanneer 'n onderdeel ontbreek, word dit 'n genoem skrapping (as dit onder 'n mikroskoop sigbaar is) en a mikrodelesie (as dit te klein is om sigbaar te wees). Mikrodelesies is so klein dat hulle slegs 'n paar gene op 'n chromosoom kan betrek.

Sommige genetiese afwykings wat deur delesies en mikrodelesies veroorsaak word, sluit in Wolf-Hirschhorn-sindroom (affekteer chromosoom 4), Cri-du-chat-sindroom (chromosoom 5), DiGeorge-sindroom (chromosoom 22) en Williams-sindroom (chromosoom 7).

In translokasies (wat ongeveer 1 uit elke 400 pasgeborenes affekteer), skuif stukkies chromosome van een chromosoom na 'n ander. Die meeste translokasies is "gebalanseerd", wat beteken dat daar geen wins of verlies aan genetiese materiaal is nie. Maar sommige is "ongebalanseerd", wat beteken dat daar op sommige plekke te veel genetiese materiaal kan wees en op ander nie genoeg nie. Met inversies (wat ongeveer 1 uit elke 100 pasgeborenes affekteer), lyk asof klein dele van die DNS-kode uitgeknip, omgedraai en weer ingesit word. Translokasies kan óf van 'n ouer geërf word óf spontaan in 'n kind se eie chromosome plaasvind.

Beide gebalanseerde translokasies en inversies veroorsaak gewoonlik geen misvormings of ontwikkelingsprobleme by die kinders wat dit het nie. Diegene met óf translokasies óf inversies wat ouers wil word, kan egter 'n verhoogde risiko van miskraam of chromosoomafwykings in hul eie kinders hê. Ongebalanseerde translokasies of inversies word geassosieer met ontwikkelings- en/of fisiese abnormaliteite.

Sekschromosome

Genetiese probleme kom ook voor wanneer abnormaliteite die geslagschromosome beïnvloed. Normaalweg sal 'n kind 'n man wees as hy een X-chromosoom van sy ma en een Y-chromosoom van sy pa erf. ’n Kind sal ’n vrou wees as sy ’n dubbele dosis X (een van elke ouer) en geen Y erf nie.

Soms word kinders egter gebore met slegs een geslagschromosoom (gewoonlik 'n enkele X) of met 'n ekstra X of Y. Meisies met Turner-sindroom word met slegs een X-chromosoom gebore, terwyl seuns met Klinefelter-sindroom met 1 of meer ekstra gebore word X-chromosome (XXY of XXXY).

Soms is dit ook 'n genetiese probleem X-gekoppel, wat beteken dat dit geassosieer word met 'n abnormaliteit wat op die X-chromosoom gedra word. Broos X-sindroom, wat intellektuele gestremdheid by seuns veroorsaak, is een so 'n afwyking. Ander siektes wat deur abnormaliteite op die X-chromosoom veroorsaak word, sluit in hemofilie en Duchenne-spierdistrofie.

Wyfies kan dalk draers van hierdie siektes wees, maar omdat hulle ook 'n normale X-chromosoom erf, word die uitwerking van die geenverandering tot die minimum beperk. Mans, aan die ander kant, het net een X-chromosoom en is byna altyd diegene wat die volle uitwerking van die X-gekoppelde versteuring toon.

Gene mutasies

Sommige genetiese probleme word veroorsaak deur 'n enkele geen wat teenwoordig is, maar op een of ander manier verander het. Sulke veranderinge in gene word genoem mutasies. Wanneer daar 'n mutasie in 'n geen is, is die aantal en voorkoms van die chromosome gewoonlik steeds normaal.

Om die gebrekkige geen vas te stel, gebruik wetenskaplikes gesofistikeerde DNS-toetstegnieke. Genetiese siektes wat deur 'n enkele probleemgeen veroorsaak word, sluit in fenielketonurie (PKU), sistiese fibrose, sekelselsiekte, Tay-Sachs-siekte en achondroplasie ('n tipe dwergisme).

Alhoewel kenners vroeër gedink het dat nie meer as 3% van alle menslike siektes deur foute in 'n enkele geen veroorsaak word nie, toon nuwe navorsing dat dit 'n onderskatting is. Binne die laaste paar jaar het wetenskaplikes genetiese skakels ontdek met baie verskillende siektes wat nie oorspronklik as geneties beskou is nie, insluitend Parkinson se siekte, Alzheimer se siekte, hartsiektes, diabetes en verskeie verskillende soorte kanker. Daar word vermoed dat veranderinge in hierdie gene 'n mens se risiko verhoog om hierdie toestande te ontwikkel.

Onkogene (kankerveroorsakende gene)

Navorsers het ongeveer 50 kankerveroorsakende gene geïdentifiseer wat 'n persoon se kans om kanker te ontwikkel aansienlik verhoog. Deur gesofistikeerde toetse te gebruik, kan dokters dalk identifiseer wie hierdie genetiese mutasies het, en bepaal wie in gevaar is.

Byvoorbeeld, wetenskaplikes het vasgestel dat kolorektale kanker soms geassosieer word met mutasies in 'n geen genaamd APC. Hulle het ook ontdek dat abnormaliteite in die BRCA1- en BRCA2-geen vroue 'n 50%-kans gee om borskanker te ontwikkel en 'n verhoogde risiko vir eierstokgewasse.

Mense wat nou bekend is dat hulle hierdie geenmutasies het, kan noukeurig deur hul dokters gemonitor word. As probleme ontwikkel, is hulle meer geneig om vroeër vir kanker behandel te word as wanneer hulle nie geweet het van hul risiko nie, en dit kan hul kans op oorlewing verhoog.

Nuwe ontdekkings, beter sorg

Wetenskaplikes het die afgelope twee dekades groot vordering gemaak op die gebied van genetika. Die kartering van die menslike genoom en die ontdekking van baie siekte-veroorsakende gene het gelei tot 'n beter begrip van die menslike liggaam. Dit het dokters in staat gestel om beter sorg aan hul pasiënte te verskaf en om die lewenskwaliteit te verhoog vir mense (en hul gesinne) wat met genetiese toestande leef.


Oorsake en Risikofaktore

  • Die ekstra chromosoom 21 lei tot die fisiese kenmerke en ontwikkelingsuitdagings wat onder mense met Downsindroom kan voorkom. Navorsers weet dat Downsindroom deur 'n ekstra chromosoom veroorsaak word, maar niemand weet met sekerheid hoekom Downsindroom voorkom of hoeveel verskillende faktore 'n rol speel nie.
  • Een faktor wat die risiko verhoog om 'n baba met Down-sindroom te hê, is die moeder se ouderdom. Vroue wat 35 jaar of ouer is wanneer hulle swanger raak, is meer geneig om 'n swangerskap te hê wat deur Down-sindroom geraak word as vroue wat op 'n jonger ouderdom swanger raak. 3-5 Die meerderheid babas met Downsindroom word egter by moeders jonger as 35 jaar oud gebore, want daar is baie meer geboortes onder jonger vroue. 6,7

Om 'n baba te hê na ouderdom 35: Hoe veroudering vrugbaarheid en swangerskap beïnvloed

'n Vrou se piek voortplantingsjare is tussen die laat tienerjare en laat 20's. Teen ouderdom 30 begin vrugbaarheid (die vermoë om swanger te raak) afneem. Hierdie afname word vinniger sodra jy jou middel-30's bereik. Teen 45 het vrugbaarheid so afgeneem dat dit vir die meeste vroue onwaarskynlik is om natuurlik swanger te raak.

Vroue begin die lewe met 'n vaste aantal eiers in hul eierstokke. Die aantal eiers neem af namate vroue ouer word. Die oorblywende eiers by ouer vroue is ook meer geneig om abnormale chromosome te hê. En namate vroue ouer word, loop hulle 'n groter risiko van afwykings wat vrugbaarheid kan beïnvloed, soos uteriene fibroïede en endometriose.

Vir gesonde paartjies in hul 20's en vroeë 30's sal ongeveer 1 uit 4 vroue in enige enkele menstruele siklus swanger raak. Teen die ouderdom van 40 sal ongeveer 1 uit 10 vroue per menstruele siklus swanger raak. 'n Man se vrugbaarheid neem ook af met ouderdom, maar nie so voorspelbaar nie.

Vroue wat later in die lewe swanger raak, het 'n groter risiko vir komplikasies. Byvoorbeeld, swanger vroue ouer as 40 het 'n verhoogde risiko van preeklampsie. Swangerskap later in die lewe kan ook die gesondheid van die fetus beïnvloed.

Ouer vroue is geneig om meer gesondheidsprobleme te hê as jonger vroue. Byvoorbeeld, hoë bloeddruk is meer algemeen by ouer mense. Om hoë bloeddruk voor swangerskap te hê, kan die risiko van preeklampsie verhoog. Maar studies toon ook dat ouer vroue wat geen gesondheidstoestande het nie, steeds ingewikkelde swangerskappe kan hê.

Die algehele risiko om 'n baba met 'n chromosoomafwyking te hê, is klein. Maar soos 'n vrou ouer word, verhoog die risiko om 'n baba te hê met ontbrekende, beskadigde of ekstra chromosome.

Down-sindroom (trisomie 21) is die mees algemene chromosoomprobleem wat met latere bevalling voorkom. Die risiko om 'n swangerskap te hê wat deur Downsindroom geraak word, is

Kom meer te wete oor toetse wat na genetiese afwykings kyk:

Voorgeboortelike siftingstoetse bepaal die risiko dat 'n swangerskap deur 'n spesifieke geboortedefek of genetiese afwyking beïnvloed sal word. Sifting kan voor en tydens swangerskap gedoen word.

Voorgeboortelike diagnostiese toetse kan vasstel of 'n swangerskap deur 'n spesifieke geboortedefek of genetiese afwyking beïnvloed word.

Beide siftings- en diagnostiese toetse word aan alle swanger vroue gebied. Jy hoef nie 'n sekere ouderdom te wees of 'n familiegeskiedenis van 'n afwyking te hê om hierdie toetse te ondergaan nie. Dit is jou keuse of jy dit wil laat doen. Praat met jou verloskundige en ginekoloog (ob-gyn) oor genetiese toetsopsies sodat jy 'n keuse kan maak wat reg is vir jou.

Die risiko's van miskraam en stilgeboorte is groter by vroue wat ouer as 35 is. Ook meervoudige swangerskap is meer algemeen by ouer vroue as by jonger vroue. Soos die eierstokke verouder, is dit meer geneig om meer as een eier elke maand vry te stel.

Sommige vrugbaarheidsbehandelings verhoog ook die kans op 'n meervoudige swangerskap. Alhoewel meervoudige swangerskappe gesond kan wees, kan hierdie swangerskappe die risiko van premature geboorte verhoog.

Alle vroue moet dink of hulle graag kinders wil hê en, indien wel, wanneer om hulle te hê. Dit word 'n reproduktiewe lewensplan genoem. As jy eendag kinders wil hê, kan jou plan 'n eenvoudige stelling wees soos: &ldquo ek wil skool klaarmaak en meer geld spaar voordat ek kinders kry&rdquo of &ldquo ek wil graag kinders in my 20's hê wanneer my kanse vir 'n gesonde swangerskap is beste.&rdquo Om met jou ob-gyn te praat, kan jou help om jou voortplantingsleweplan te ontwikkel. Die volgende stap is om jou plan in werking te stel.

As jy nie swanger wil raak nie en 'n manlike maat het, gebruik 'n geboortebeperkingsmetode om swangerskap te voorkom. Maak seker dat jy 'n metode gebruik wat pas by jou voortplantingsdoelwitte, jou lewenstyl en enige gesondheidstoestande wat jy het. Saam kan jy en jou ob-gyn jou geboortebeperkingsopsies hersien.

As jy binnekort swanger wil raak, moet jy probeer om so gesond as moontlik te wees voor swangerskap. Neem stappe om op te hou om alkohol, tabak en dagga te gebruik. Jy moet ook begin om 'n prenatale vitamien met foliensuur te gebruik om neuraalbuisdefekte (NTD's) te voorkom.

Dit is 'n besoek met jou ob-gyn wat jou help om vir 'n swangerskap te beplan. Tydens hierdie besoek moet jou ob-gyn jou mediese geskiedenis, jou familiegeskiedenis, enige vorige swangerskappe en enige medikasie wat jy neem, hersien. U moet ook immuniserings hersien om seker te maak dat u al die entstowwe het wat vir u aanbeveel word. Jy en jou ob-gyn kan ook praat oor

hoe jy 'n gesonde gewig kan handhaaf voordat jy swanger raak

die opsie van draersifting vir jou en, indien nodig, jou maat

Alle vroue moet met hul ob-gyns praat voordat hulle probeer om swanger te word, maar dit is veral belangrik vir vroue ouer as 35.

Dit is 'n goeie idee om een ​​keer per jaar met jou ob-gyn oor jou plan te praat. Vra jouself af of jy in die volgende jaar kinders wil hê. As jou antwoord ja is, kan jy stappe doen vir 'n gesonde swangerskap. As jou antwoord nee is, kan jy seker maak dat jy 'n betroubare geboortebeperkingsmetode gebruik.

Tans is daar geen mediese tegniek wat kan waarborg dat vrugbaarheid behoue ​​sal bly nie. As jy weet dat jy later in jou lewe kinders wil hê, kan een opsie in vitro-bevrugting (IVF) wees. Met IVF word sperm met 'n vrou se eiers in 'n laboratorium gekombineer. As die sperm die eiers bevrug, kan embrio's groei.

Embrio's kan gevries word en baie jare later gebruik word. Wanneer jy gereed is, kan 'n embrio na jou baarmoeder oorgeplaas word om 'n swangerskap te probeer bereik. Die kans dat IVF vir jou sal werk hang af van baie faktore, insluitend jou gesondheid en jou ouderdom wanneer die embrio's gevries word.

Om met 'n vrugbaarheidskenner te praat, sal jou help om jou kanse op sukses met IVF te verstaan. Daar is ook finansiële oorwegings. Sommige IVF-behandelings is duur en word moontlik nie deur versekering gedek nie.

'n Prosedure genaamd oösiet cryopreservation&mdash&ldquovries jou eiers&rdquo&mdash het in onlangse jare meer gewild geword. In hierdie prosedure word verskeie eiers uit die eierstokke verwyder. Die onbevrugte eiers word dan gevries vir latere gebruik in IVF.

Bevriesing van eiers lyk dalk na 'n goeie opsie vir vroue wat die kraam wil vertraag. Maar eiervries word hoofsaaklik aanbeveel vir vroue wat kankerbehandeling het wat hul toekomstige vrugbaarheid sal beïnvloed. Daar is nie genoeg navorsing om roetine-vriesing van eiers aan te beveel met die uitsluitlike doel om kinders te baar nie. Eiervries is ook duur en word dalk nie deur versekering gedek nie.

As jy ouer as 35 is en nie swanger geraak het na 6 maande van gereelde seks sonder om geboortebeperking te gebruik nie, praat met jou ob-gyn oor 'n onvrugbaarheidsevaluering. As jy ouer as 40 is, word 'n evaluering aanbeveel voordat jy probeer om swanger te raak. Hierdie advies is veral waar as jy 'n probleem het wat vrugbaarheid kan beïnvloed, soos endometriose.

Tydens 'n evaluering het jy fisiese eksamens en toetse om die oorsaak van onvrugbaarheid te probeer vind. As 'n oorsaak gevind word, kan behandeling moontlik wees. In baie gevalle kan onvrugbaarheid suksesvol behandel word, selfs al word geen oorsaak gevind nie. Maar die kanse op sukses met hierdie behandelings neem af met ouderdom. Sien Evaluering van onvrugbaarheid vir meer inligting.

Om vroeë en gereelde voorgeboortesorg te kry, kan jou kanse op 'n gesonde baba verhoog. By elke besoek moet jou gesondheid en jou fetus se gesondheid gemonitor word. As jy 'n reeds bestaande mediese toestand het of as 'n mediese toestand tydens swangerskap ontwikkel, moet jy dalk jou ob-gyn meer gereeld sien. Gereelde voorgeboortesorg kan jou ob-gyn help om probleme gouer te vind en stappe te doen om dit te help bestuur.

Draerondersoek: 'n Toets wat op 'n persoon gedoen word sonder tekens of simptome om uit te vind of hy of sy 'n geen vir 'n genetiese afwyking dra.

Chromosome: Strukture wat binne elke sel in die liggaam geleë is. Hulle bevat die gene wat 'n persoon se fisiese samestelling bepaal.

Komplikasies: Siektes of toestande wat voorkom as gevolg van 'n ander siekte of toestand. ’n Voorbeeld is longontsteking wat as gevolg van griep voorkom. 'n Komplikasie kan ook voorkom as gevolg van 'n toestand, soos swangerskap. 'n Voorbeeld van 'n swangerskapskomplikasie is premature kraam.

Diagnostiese toetse: Toetse wat soek na 'n siekte of oorsaak van 'n siekte.

Downsindroom (Trisomie 21): 'n Genetiese afwyking wat abnormale kenmerke van die gesig en liggaam, mediese probleme soos hartdefekte en verstandelike gestremdheid veroorsaak. Die meeste gevalle van Down-sindroom word veroorsaak deur 'n ekstra chromosoom 21 (trisomie 21).

Eiers: Die vroulike voortplantingselle gemaak in en vrygestel uit die eierstokke. Ook genoem die eierselle.

Embrio's: Die stadium van voorgeboortelike ontwikkeling wat by bevrugting begin (samevoeging van 'n eiersel en sperm) en duur tot 8 weke.

Endometriose: 'n Toestand waarin weefsel wat die baarmoeder beklee, buite die baarmoeder gevind word, gewoonlik op die eierstokke, fallopiese buise en ander bekkenstrukture.

Fetus: Die stadium van menslike ontwikkeling na 8 voltooide weke na bevrugting.

Fibroïede: Groeisels wat in die spier van die baarmoeder vorm. Fibroïede is gewoonlik nie-kankeragtig.

Foliensuur: ’n Vitamien wat die risiko van sekere geboortedefekte verminder wanneer dit voor en tydens swangerskap geneem word.

Genetiese afwykings: Afwykings wat veroorsaak word deur 'n verandering in gene of chromosome.

Hoë bloeddruk: Bloeddruk bo die normale vlak. Ook genoem hipertensie.

In vitro-bevrugting (IVF): 'n Prosedure waarin 'n eiersel uit 'n vrou se eierstok verwyder word, in 'n laboratorium met die man se sperm bevrug word, en dan na die vrou se baarmoeder oorgeplaas word om 'n swangerskap te verkry.

Menstruele siklus: Die maandelikse proses van veranderinge wat plaasvind om 'n vrou se liggaam voor te berei vir moontlike swangerskap. 'n Menstruele siklus word gedefinieer as die eerste dag van menstruele bloeding van een siklus tot die eerste dag van menstruele bloeding van die volgende siklus.

Miskraam: Verlies van 'n swangerskap wat in die baarmoeder is.

Meervoudige swangerskap: 'n Swangerskap waar daar twee of meer fetusse is.

Neuralebuisdefekte (NTD's): Geboortedefekte wat voortspruit uit 'n probleem in die ontwikkeling van die brein, rugmurg of hul bedekkings.

Verloskundige&ndashGinekoloog (Ob-Gyn): 'N Dokter met spesiale opleiding en opleiding in vroue se gesondheid.

Oosiet kriopreservering: 'n Prosedure waarin eiers van 'n vrou se eierstokke verwyder en gevries word vir latere gebruik met in vitro-bevrugting (IVF).

Eierstokke: Organe in vroue wat die eiers bevat wat nodig is om swanger te raak en belangrike hormone te maak, soos estrogeen, progesteroon en testosteroon.

Preeklampsie: 'n Versteuring wat tydens swangerskap of na bevalling kan voorkom waarin daar hoë bloeddruk en ander tekens van orgaanbesering is. Hierdie tekens sluit in 'n abnormale hoeveelheid proteïene in die urine, 'n lae aantal bloedplaatjies, abnormale nier- of lewerfunksie, pyn oor die boonste buik, vloeistof in die longe, of 'n erge hoofpyn of veranderinge in visie.

Voorgeboortelike sorg: 'n Program van sorg vir 'n swanger vrou voor die geboorte van haar baba.

Premature: Minder as 37 weke van swangerskap.

Siftingstoetse: Toetse wat kyk vir moontlike tekens van siekte by mense wat nie tekens of simptome het nie.

Seksueel oordraagbare infeksies (SOI's): Infeksies wat deur seksuele kontak versprei word. Infeksies sluit in chlamydia, gonorree, menslike papillomavirus (HPV), herpes, sifilis en menslike immuniteitsgebrekvirus (MIV, die oorsaak van verworwe immuniteitsgebreksindroom [VIGS]).

Sperm: 'n Sel wat in die manlike testikels gemaak word wat 'n vroulike eiersel kan bevrug.

Stilgeboorte: Geboorte van 'n dooie fetus.

Uterus: 'n Spierorgaan in die vroulike bekken. Tydens swangerskap hou hierdie orgaan die fetus vas en voed dit. Ook genoem die baarmoeder.

Entstowwe: Stowwe wat die liggaam help om siektes te beveg. Entstowwe word gemaak van baie klein hoeveelhede swak of dooie middels wat siektes veroorsaak (bakterieë, gifstowwe en virusse).


Oorsig van Huntington se siekte

HD affekteer die hele brein, maar sekere areas is meer kwesbaar as ander. Hierbo in blou is die striatum - 'n area diep in die brein wat 'n sleutelrol speel in beweging, bui en gedragsbeheer. Die striatum is die deel van die brein wat die meeste deur HD geraak word.

Wat is Huntington se siekte?

Huntington se siekte (HD) is 'n breinsiekte wat van geslag tot geslag in families oorgedra word. Dit word veroorsaak deur 'n fout in die DNS-instruksies wat ons liggame bou en aan die gang hou. DNS bestaan ​​uit duisende gene, en mense met HD het 'n klein fout in een geen, genaamd huntingtin. Met verloop van tyd veroorsaak hierdie fout skade aan die brein en lei tot HD-simptome.

HD veroorsaak agteruitgang in 'n persoon se fisiese, geestelike en emosionele vermoëns, gewoonlik gedurende hul eerste werksjare, en het tans geen genesing nie. Die meeste mense begin simptome ontwikkel tydens volwassenheid, tussen die ouderdom van 30 tot 50, maar HD kan ook by kinders en jong volwassenes voorkom (bekend as jeugdige HD of JHD). HD staan ​​bekend as 'n gesinsiekte omdat elke kind van 'n ouer met HD 'n 50/50 kans het om die foutiewe geen te erf. Vandag is daar ongeveer 41 000 simptomatiese Amerikaners en meer as 200 000 loop die risiko om die siekte te erf.

Simptome van Huntington’ se siekte

Die simptome van HD kan baie van persoon tot persoon verskil, maar dit sluit gewoonlik in:

  • Persoonlikheidsveranderinge, buierigheid en depressie
  • Vergeetagtigheid en verswakte oordeel
  • Onstabiele gang en versterk onwillekeurige bewegings (chorea)
  • Onduidelike spraak, probleme om te sluk en aansienlike gewigsverlies

Die meeste mense met HD ervaar probleme met denke, gedrag en bewegings. Simptome vererger gewoonlik in die loop van 10 tot 25 jaar en beïnvloed die vermoë om te redeneer, loop en praat. Vroegtydig kan 'n persoon met HD of hul vriende en familie probleme opmerk met beplanning, onthou en aanhou taak. Hulle kan gemoedsveranderinge soos depressie, angs, prikkelbaarheid en woede ontwikkel. Die meeste mense met HD raak "fieterig" en ontwikkel bewegings van die gesig en ledemate bekend as chorea, wat hulle nie kan beheer nie.

As gevolg van die onbeheerde bewegings (chorea), kan 'n persoon met HD baie gewig verloor sonder om van plan te wees, en kan dit moeilik wees om te loop, balanseer en veilig rond te beweeg. Hulle sal uiteindelik die vermoë verloor om te werk, bestuur en take by die huis te bestuur, en kan kwalifiseer vir ongeskiktheidsvoordele. Met verloop van tyd sal die individu probleme ontwikkel met praat en sluk, en hul bewegings sal stadig en styf word. Mense met gevorderde HD benodig voltydse sorg om te help met hul daaglikse aktiwiteite, en hulle swig uiteindelik aan longontsteking, hartversaking of ander komplikasies. Die simptome van HD word soms beskryf as ALS, Parkinson's en Alzheimer's - gelyktydig.

Die Huntingtin-geen en proteïen

Die DNS-fout wat HD veroorsaak, word gevind in 'n geen genaamd huntingtin. Hierdie geen is in 1993 ontdek. Almal het die huntingtin-geen, maar net diegene wat die fout, bekend as die HD-mutasie, erf, sal HD ontwikkel en die risiko loop om dit aan hul kinders oor te dra. Genes are made up of the nucleotide “letters” A,G,C, and T, which form a code that is read in groups of three. HD is caused by a stretch of the letters C-A-G in the huntingtin gene which repeat over and over, too many times…CAGCAGCAGCAGCAG. This is known as a CAG repeat expansion. In the huntingtin gene, most people have around 20 CAG repeats, but people with HD have around 40 or more. Every person who has this CAG repeat expansion in the HD gene will eventually develop the disease, and each of their children has a 50% chance of developing HD.

Our genes are like an instruction manual for making proteins, the machines that run everything in our bodies. The huntingtin gene (DNA) contains instructions that are copied into a biological message (RNA) which makes the huntingtin protein. The huntingtin protein is very large and seems to have many functions, especially as the brain is developing before birth, but it is not fully understood. We know that the extra CAG repeats in people with HD cause the huntingtin protein to be extra-long and difficult to maintain, which makes it difficult for it to do its job. Over many years, this “mutant” huntingtin protein forms clumps in brain cells, and causes them to become damaged and die. The most vulnerable part of the brain in HD is called the striatum, and it controls movement, mood, and memory. Damage to the striatum over time is what causes the symptoms of HD.

Treating Huntington’s Disease

There is currently no cure or treatment which can halt, slow or reverse the progression of the disease. However, there are many treatments and interventions that can help to manage HD symptoms. A neurologist, psychiatrist, or nurse with expertise in HD may prescribe medications to ease anxiety and depression, help with troublesome

behaviors, and calm uncontrolled movements. A psychologist or social worker can provide individual or group counseling. Physical and occupational therapists can work with patients and families to develop strength, move safely, and adjust the home environment and activities as needed. Speech language pathologists and nutritionists can help with communication, eating and swallowing safely, and combating weight loss. Clinician researchers may suggest participation in HD clinical trials.

Social and community support is an important part of HD care. Family, friends, loved ones, and companions often assume many of the HD person’s former responsibilities and help with daily activities and care routines when they can no longer do so themselves. Caregivers and kids may also need support for the challenges and stresses that come with HD.


Impact of Tourette syndrome

Having TS can have an impact on many areas of life, particularly when children have another condition in addition to TS. Using data from CDC studies, the following are examples of the impact of TS.

Onderwys

Compared to children without TS, children with TS were more likely to 5

  • Have an individualized education program (IEP)
  • Have a parent contacted about school problems and
  • Not complete their homework.

Once the presence of other disorders was taken into account, children with TS were still more likely to have an IEP compared to children without TS.

Health and healthcare

Compared to children without TS, children with TS were more likely to have 6

  • A chronic health condition
  • A special healthcare need
  • Received mental health treatment and
  • Needs for mental health care that were not met.

Compared to children without TS, children with TS were less likely to have

Parenting

Compared to children without TS, children with TS were more likely to have parents with high levels of stress and frustration. 7

Once the presence of other disorders was taken into account, parents of children with Tourette were still more likely to have high levels of stress and frustration.

Social competence

Compared to children without TS, children with TS were more likely to struggle with 8

  • Social competence
  • Higher levels of behavioral problems and
  • Lower levels of social skills.

This is particularly true when children have moderate-to-severe TS and when they are diagnosed with other mental, emotional, or behavioral disorders.

Bullying involvement

Compared to children without TS, children with TS were 2

  • More likely to be the victim of bullying
  • More likely to be the perpetrator of bullying and
  • More likely to be both a victim and a perpetrator.

Bullying is most common among peers, but children with TS also experience being treated differently by teachers and other adults. 9


Genetic causality in mental disorders

As of 2002, genes appear to influence the development of mental disorders in three major ways: they may govern the organic causes of such disorders as Alzheimer's disease and schizophrenia they may be responsible for abnormalities in a person's development before or after birth and they may influence a person's susceptibility to anxiety, depression, personality disorders , and substance abuse disorders.

One technological development that has contributed to the major advances in biological psychiatry in the last twenty years is high-speed computing. Faster computers have enabled researchers to go beyond rough estimates of the heritability of various disorders to accurate quantification of genetic effects. In some cases the data have led to significant reappraisals of the causes of specific disorders. As recently as the 1960s and 1970s, for example, schizophrenia was generally attributed to "refrigerator mothers" and a chilly emotional climate in the patients' extended families. As of 2002, however, the application of computer models to schizophrenia indicates that the heritability of the disorder may be as high as 80%. Another instance is autism , which was also blamed at one time on faulty parenting but is now known to be 90+% heritable.

Mental disorders with organic causes

The two most important examples of mental disorders caused by organic changes or abnormalities in the brein are late-onset Alzheimer's disease and schizophrenia. Both disorders are polygenic , which means that their expression is determined by more than one gene. Another disorder that is much less common, Huntington's disease, is significant because it is one of the few mental disorders that is monogenies , or determined by a single gene.

SCHIZOPHRENIA. Researchers have known for many years that first-degree biological relatives of patients with schizophrenia have a 10% risk of developing the disorder, as compared with 1% in the general population. The identical twin of a person with schizophrenia has a 40%&ndash50% risk. The first instance of a specific genetic linkage for schizophrenia, however, was discovered in 1987 by a group of Canadian researchers at the University of British Columbia. A case study that involved a Chinese immigrant and his 20-year-old nephew, both diagnosed with schizophrenia, led the researchers to a locus on the short arm of chromosome 5. In 1988, a study of schizophrenia in several Icelandic and British families also pointed to chromosome 5. Over the course of the next decade, other studies of families with a history of schizophrenia indicated the existence of genes related to the disorder on other chromosomes. In late 2001, a multidisciplinary team of researchers reported positive associations for schizophrenia on chromosomes 15 and 13. Chromosome 15 is linked to schizophrenia in European American families as well as some Taiwanese and Portuguese families. A recent study of the biological pedigrees found among the inhabitants of Palau (an isolated territory in Micronesia) points to chromosomes 2 and 13. Still another team of researchers has suggested that a disorder known as 22q deletion syndrome may actually represent a subtype of schizophrenia, insofar as people with this syndrome have a 25% risk of developing schizophrenia.

ALZHEIMER'S DISEASE. Late-onset Alzheimer's disease (AD) is unquestionably a polygenic disorder. It has been known since 1993 that a specific form of a gene for apolipoprotein E (apoE4) on human chromosome 19 is a genetic risk factor for late-onset Alzheimer's. People who have the apoE4 gene from one parent have a 50% chance of developing AD a 90% chance if they inherited the gene from both parents. They are also likely to develop AD earlier in life. One of the remaining puzzles about this particular gene, however, is that it is not a consistent marker for AD. In other words, some people who have the apoE4 gene do not develop Alzheimer's, and some who do not have the gene do develop the disorder. In 1998, another gene on chromosome 12 that controls the production of bleomycin hydrolase (BH) was identified as a second genetic risk factor that acts independently of the apoE gene. In December 2000, three separate research studies reported that a gene on chromosome 10 that may affect the processing of amyloid-beta protein is also involved in the development of late-onset AD.

There are two other forms of AD, early-onset AD and familial Alzheimer's disease (FAD), which have different patterns of genetic transmission. Early-onset AD is caused by a defect in one of three genes known as APP, presenilin-1, and presenilin-2, found on human chromosomes 21, 14, and 1, respectively. Early-onset AD is also associated with Down syndrome, in that persons with trisomy 21 (three forms of human chromosome 21 instead of a pair) often develop this form of Alzheimer's. The brains of people with Down syndrome age prematurely, so that those who develop early-onset AD are often only in their late 40s or early 50s when the symptoms of the disease first appear. Familial Alzheimer's disease appears to be related to abnormal genes on human chromosomes 21 and 14.

HUNTINGTON'S DISEASE. Huntington's disease, or Huntington's chorea, is a neurological disorder that kills the cells in the caudate nucleus, the part of the brain that coordinates movement. It also destroys the brain cells that control cognitive functions. In 1983, the gene that causes Huntington's disease was discovered on the short arm of human chromosome 4. Ten years later, the gene was identified as an instance of a triplet or trinucleotide repeat. Nucleotides are the molecular "building blocks" of DNA and RNA. Three consecutive nucleotides form a codon, or triplet, in messenger RNA that codes for a specific amino acid. In 1991, researchers discovered not only that nucleotide triplets repeat themselves, but that these repetitions sometimes expand in number during the process of genetic transmission. This newly discovered type of mutation is known as a dynamic or expansion mutation. Since 1991, more than a dozen diseases have been traced to expansion mutations. Eight of them are caused by repeats of the triplet cytosine-adenine-guanine (CAG), which codes for an amino acid called glutamine. In 1993, Huntington's disease was identified as a CAG expansion mutation disorder. Where the genetic material from a normal chromosome 4 has about 20 repeats of the CAG triplet, the Huntington's gene has a minimum of 45 repeats, sometimes as many as 86. The higher the number of CAG triplet repeats in a Huntington's gene, the earlier the age at which the symptoms will appear. The expansion mutation in Huntington's disease results in the production of a toxic protein that destroys the cells in the patient's brain that control movement and cognition.

Childhood developmental disorders

Developmental disorders of childhood are another large category of mental disorders caused by mutations, deletions, translocations (rearrangements of the arms of chromosomes) and other alterations in genes or chromosomes.

TRIPLET REPEAT DISORDERS. Since 1991, expansion mutations have been identified as the cause of thirteen different diseases. Some, like Huntington's disease, are characterized by long expansion mutations of the trinucleotide sequence CAG, which in effect adds so much glutamine to the protein being synthesized that it becomes toxic to the nervous system. A second category of triplet repeat disorders contains extra triplets that add an amino acid called alanine to the protein. The sequence of nucleotides is cytosine-guanine-N, where N stands for any of the four basic nucleotides. Although the proteins produced by this type of expansion mutation are not toxic, their normal function in the body is disrupted. The developmental disorders related to these CGN triplets are characterized by abnormalities of the skeleton. One of these disorders is synpolydactyly, in which the patient has more than the normal number of fingers or toes. Another is cleidocranial dysplasia, a disorder marked by abnormal development of the skull.

Other developmental disorders are caused by expansion mutations outside the regions of the gene that code for proteins. The segments of DNA that specify the sequence of a portion of a protein are known as exons , while the stretches of DNA that lie between the exons and do not code for proteins are called introne . The CAG and CGN groups of triplet disorders described in the preceding paragraph are expansion mutations that occur within exons. A third group of triplet disorders results from expansion mutations in introns. Expansions in this third group are usually much longer than those in the first two categories some repeat several hundred or even several thousand times. The best-known expansion mutation in this group causes the disorder known as fragile X syndrome. Fragile X syndrome is the most common inherited form of mental retardation and should be considered in the differential diagnosis of any child with developmental delays, mental retardation, or learning difficulties. The syndrome is caused by a large expansion of a cytosine-guanine-guanine (CGG) repeat which interferes with normal protein transcription from a gene called the FMR1 gene on the X chromosome. Males with the mutation lack a second normal copy of the gene and are more severely affected than females who have a normal FMR1 gene on their second X chromosome. In both sexes there is a correlation between the length of the expansion mutation and the severity of the syndrome.

The discovery of expansion mutations was the solution to a long-standing genetic riddle. Clinicians had noticed as early as 1910 that some disorders produce a more severe phenotype or occur at earlier and earlier ages in each successive generation of an affected family. This phenomenon is known as anticipation , but its biological basis was not understood until recently. It is now known that triplet repeats that are long enough to cause disorders are unstable and tend to grow longer from generation to generation. For example, an expansion mutation of the cytosine-thymine-guanine (CTG) triplet causes a potentially life-threatening developmental disorder known as myotonic dystrophy. Repeats of the CTG triplet that are just above the threshold for myotonic dystrophy itself may produce a relatively mild disorder, namely eye cataracts in later life. Within two to three generations, however, the CTG repeats become longer, producing a fatal congenital illness. In addition to developmental disorders of childhood, expansion mutations may also be involved in other psychiatric disorders. Anticipation has been found in some families affected by bipolêre versteuring and schizophrenia, and some researchers think that it may also be present in some forms of autism.

GENOMIC IMPRINTING. Another recent discovery in the field of biological psychiatry is the phenomenon of genomic imprinting, which distinguishes between chromosomes derived from a person's father and those derived from the mother. Genomic imprinting was discovered in the late 1980s as an exception to Gregor Mendel's laws of biological inheritance. A small subset of human genes are expressed differently depending on the parent who contributes them to a child's genetic makeup. This phenomenon has helped researchers understand the causation of three well-known genetic disorders&mdash Prader-Willi, Angelman, and Beckwith-Wiedemann syndromes.

In the 1980s, researchers studying Prader-Willi syndrome and Angelman syndrome noticed that both disorders were caused by a deletion on the long arm of chromosome 15 in the very same region, extending from 15q11 to 15q13. This finding was surprising, because the two syndromes have markedly different phenotypes. Children with Prader-Willi syndrome have severe mental retardation, poor muscle tone, small hands and feet, and a voracious appetite (hyperphagia) that begins in childhood. As a result, they are often obese by adolescence. Children with Angelman syndrome, on the other hand, do not speak, are often hyperactive, and suffer from seizures and sleep disturbances. In the late 1980s, advances in molecular genetics revealed that the different expressions of the same deletion on the same chromosome were determined by the sex of the parent who contributed that chromosome. Children with Prader-Willi syndrome had inherited their father's copy of chromosome 15 while the children with Angelman syndrome had inherited their mother's. Highly specific diagnostic tests for these two disorders have been developed within the past decade.

Beckwith-Wiedemann syndrome is an overgrowth condition in which patients develop abnormally large bodies. They often have low blood sugar at birth and are at high risk for developing Wilms tumor, a childhood form of kidney cancer. Beckwith-Wiedemann syndrome is caused by several different genetic mutations that affect imprinted genes on chromosome 11p15. One of these imprinted genes governs the production of a growth factor that is responsible for the children's large body size.

BEHAVIORAL PHENOTYPES. Although medical professionals are familiar with the physical phenotypes associated with genetic disorders, the notion of behavioral phenotypes is still controversial. A behavioral phenotype is the characteristic set of behaviors found in patients with a genetic disorder. Behavioral phenotypes include patterns of language usage, cognitive development, and social adjustment as well as behavioral problems in the narrow sense. It is important for psychiatrists who treat children and adolescents to understand behavioral phenotypes, because they are better able to identify problem behaviors as part of a genetic syndrome and refer children to a geneticist for an accurate genetic diagnosis.

Examples of behavioral phenotypes are those associated with Down, Prader-Willi, and Williams syndromes. Children with Down syndrome have an increased risk of developing early-onset Alzheimer's disease. They are usually quiet and good-tempered, but may also be hyperactive and impulsive. Their behavioral phenotype includes delayed language development and moderate to severe mental retardation.

Children with Prader-Willi syndrome are often quiet in childhood but develop stubborn, aggressive, or impulsive patterns of behavior as they grow older. The onset of their hyperphagia is often associated with temper tantrums and other behavioral problems. They are typically obsessed with food, frequently hoarding it, stealing it, or stealing money to buy food. About 50% of children diagnosed with Prader-Willi syndrome meet the criteria for obsessief-kompulsiewe versteuring (OCD).

Williams syndrome is a genetic disorder that results from a deletion of locus 23 on chromosome 7q11. Children with this syndrome often have an "elf-like" face with short upturned noses and small chins. Their behavioral phenotype includes talkativeness, friendliness, and a willingness to follow strangers. They are also hyperactive and easily distracted from tasks. The personality profile of children with Williams syndrome is so distinctive that many are diagnosed on the basis of the behavioral rather than the physical phenotype.

Psychological/behavioral vulnerability in adults

Although psychiatrists at one time regarded emotional wounds in early childhood as the root cause of anxiety and depressive disorders in later life, inherited vulnerability to these disturbances is the subject of intensive study at the present time. In the past two decades, genetic factors have been shown to influence the likelihood of a person's developing mood disorders or post-traumatic syndromes in adult life. A study done in 1990 showed that first-degree relatives of a person diagnosed with major depression were two to four times as likely to develop depression themselves as people in the general population. As of 2002, however, the genetic patterns involved in depression appear to be quite complex there is some evidence that both genomic imprinting and the phenomenon of anticipation may be present in some families with multigenerational histories of depression. In addition, the evidence indicates that susceptibility to major depression is governed by several different genes on several different chromosomes. At present, genetic factors are thought to account for about 40% of a person's risk of depression, with environmental factors and personal temperament accounting for the remaining 60%.

With regard to manic depression, twin studies have shown that the twin of a patient diagnosed with manic depression has a 70%&ndash80% chance of developing the disorder. As of January 2002, a team of German researchers studying 75 families with a total of 275 members diagnosed with manic depression (out of 445 persons) has narrowed its search for genes for manic depression to one locus on human chromosome 10 and another on the long arm of chromosome 8.

POST-TRAUMATIC SYNDROMES. Researchers have found that some persons are more vulnerable than others to developing dissociative and anxiety-related symptoms following a traumatic experience. Vulnerability to trauma is affected by such inherited factors as temperament as well as by family or cultural influences shy or introverted persons are at greater risk for developing post-traumatic stress disorder (PTSD) than their extroverted or outgoing peers. In addition, twin studies indicate that certain abnormalities in brain hormone levels and brain structure are inherited, and that these increase a person's susceptibility to developing acute stress disorder (ASD) or PTSD following exposure to trauma.

ANXIETY DISORDERS. It has been known for some time that anxiety disorders tend to run in families. Recent twin studies as well as the ongoing mapping of the human genome point to a genetic factor in the development of generalized anxiety disorder (GAD). One study determined the heritability of GAD to be 0.32.

Recent research has also confirmed earlier hypotheses that there is a genetic component to agoraphobia , and that it can be separated from susceptibility to panic disorder (PD). In 2001 a team of Yale geneticists reported the discovery of a genetic locus on human chromosome 3 that governs a person's risk of developing agoraphobia. Panic disorder was found to be associated with two loci, one on human chromosome 1 and the other on chromosome 11q. The researchers concluded that agoraphobia and PD are common, heritable anxiety disorders that share some but not all of their genetic loci for susceptibility.

BEHAVIORAL TRAITS. There has been considerable controversy in the past decade concerning the mapping of genetic loci associated with specific human behaviors, as distinct from behavioral phenotypes related to developmental disorders. In 1993 a group of Dutch researchers at a university-affiliated hospital in Nijmegen reported that a mutation in a gene that governs production of a specific enzyme (monoamine oxidase A or MAOA) appeared to be the cause of violent antisocial behavior in several generations of males in a large Dutch family. At least fourteen men from this family had been in trouble with the law for unprovoked outbursts of aggression, ranging from arson and attacks on employers to sexual assaults on female relatives. Tests of the men's urine indicated that neurotransmitters secreted when the body responds to stress were not being cleared from the bloodstream, which is the normal function of MAOA. In other words, the genetic mutation resulted in an overload of stress-related neurotransmitters in the men's bodies, which may have primed them to act out aggressively. As of 2002, however, the Dutch findings have not been replicated by other researchers.

Another controversial study in the early 1990s concerned the possible existence of "gay genes" as a factor in human homosexuality. A researcher at the Salk Institute found that cells in the hypothalamus, a structure in the brain associated with the regulation of temperature and sleep cycles, were over twice as large in heterosexual males as in homosexual men. Although the researcher acknowledged that the structural differences may have arisen in adult life and were not necessarily present at birth, he raised the possibility that sexual orientation may have a genetic component. Another study of affected sibling pairs reported a possible locus for a "gay gene" on the X chromosome, but as of 2002 the results have not been replicated elsewhere.

In general, however, research into the genetic component of human behavior is presently conducted with one eye, so to speak, on the social and political implications of its potential results. Given contemporary concerns about the misuse of findings related to biological race or sex, investigators are usually careful to acknowledge the importance of environmental as well as genetic factors.


Type 1 Diabetes Risk Factors

There are several risk factors that may make it more likely that you’ll develop type 1 diabetes—as you have the genetic marker that makes you susceptible to diabetes. That genetic marker is located on chromosome 6, and it’s an HLA (human leukocyte antigen) complex. Several HLA complexes have been connected to type 1 diabetes, and if you have one or more of those, you may develop type 1. (However, having the necessary HLA complex is not a guarantee that you will develop diabetes in fact, less than 10% of people with the “right” complex(es) actually develop type 1.)

Other risk factors for type 1 diabetes include:

Virale infeksies: Researchers have found that certain viruses may trigger the development of type 1 diabetes by causing the immune system to turn against the body—instead of helping it fight infection and sickness. Viruses that are believed to trigger type 1 include: German measles, coxsackie, and mumps.

Race/ethnicity: Certain ethnicities have a higher rate of type 1 diabetes. In the United States, Caucasians seem to be more susceptible to type 1 than African-Americans and Hispanic-Americans. Chinese people have a lower risk of developing type 1, as do people in South America.

Geography: It seems that people who live in northern climates are at a higher risk for developing type 1 diabetes. It’s been suggested that people who live in northern countries are indoors more (especially in the winter), and that means that they’re in closer proximity to each other—potentially leading to more viral infections.

Conversely, people who live in southern climates—such as South America—are less likely to develop type 1. And along the same lines, researchers have noticed that more cases are diagnosed in the winter in northern countries the diagnosis rate goes down in the summer.

Family history: Since type 1 diabetes involves an inherited susceptibility to developing the disease, if a family member has (or had) type 1, you are at a higher risk.

If both parents have (or had) type 1, the likelihood of their child developing type 1 is higher than if just one parent has (or had) diabetes. Researchers have noticed that if the father has type 1, the risk of a child developing it as well is slightly higher than if the mother or sibling has type 1 diabetes.

Early diet: Researchers have suggested a slightly higher rate of type 1 diabetes in children who were given cow’s milk at a very young age.

Other autoimmune conditions: As explained above, type 1 diabetes is an autoimmune condition because it causes the body’s immune system to turn against itself. There are other autoimmune conditions that may share a similar HLA complex, and therefore, having one of those disorders may make you more likely to develop type 1.

Other autoimmune conditions that may increase your risk for type 1 include: Graves' disease, multiple sclerosis, and pernicious anemia.


What diseases or injuries can cause color blindness?

Color blindness can also happen if your eyes or the part of your brain that helps you see color gets damaged. This can be caused by:

  • Eye diseases, like glaucoma or macular degeneration
  • Brain and nervous system diseases, like Alzheimer’s or multiple sclerosis
  • Some medicines, like Plaquenil (a rheumatoid arthritis medicine)
  • Eye or brain injuries

Your color vision may also get worse as you get older, especially if you get a cataract — a cloudy area on your eye.