Glossary for Medical Genetics.docx

Glossary for Medical Genetics.docx

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GlossaryforMedicalGenetics

GlossaryforMedicalGenetics

◆Allele:

oneofthealternativeversionsofageneorDNAsequenceatagivenlocus.

◆Allele-specificoligonucleotide（ASO）:

anoligonucleotideprobesynthesizedtomatchaparticularDNAsequencepreciselyandallowthediscriminationofallelesthandifferbyonlyasinglebase.

◆Allelicheterogeneity:

inapopulation,theremaybeanumberofdifferentmutantallelesatasinglelocus.Inanindividual,thesameorsimilarphenotypemaybecausedbydifferentmutantallelesratherthanbyidenticalallelesatthelocus.（血红蛋白基因突变）

◆Locusheterogeneity:

theproductionofidenticalphenotypesbymutantsattwoormoredifferentloci.（e.g.Retinitispigmentosa视网膜色素变性/先天性聋哑）

◆Amniocentesis：

aprocedureusedinprenataldiagnosistoobtainamnioticfluid,whichcontainscellsoffetaloriginthatcanbeculturedforanalysis.Amnioticfluidiswithdrawnfromtheamnioticsacbysyringeafterinsertionofahollowneedleintotheamnionthroughtheabdominalwallanduterinewall.

◆Aneuploidy:

anychromosomenumberthatisnotanexactmultipleofthehaploidnumber.Thecommonformsofaneuploidyinhumansaretrisomyandmonosomy.

◆Haploid:

thechromosomenumberofnormalgamete,withonlyonememberofeachchromosomepair.Inhumans,thehaploidnumberis23.

◆Haploinsufficiency:

acauseofgeneticdiseaseinwhichthecontributionfromanormalalleleisinsufficienttopreventdiseasebecauseofaloss-of–functionmutationattheotherallele.

◆Haplotype:

agroupofallelesincouplingatcloselylinkedloci,usuallyinheritedasaunit.

◆Hapmap:

asetofhaplotypes,definedbytagSNPs,distributedthroughoutthegenome,usedforassociationstudies.

◆Anticipation:

theprogressivelyearlieronsetandincreasedseverityofcertaindiseasesinsuccessivegenerationsofafamily.Anticipationiscausedbyexpansionofthenumberofunstablerepeatswithinthegeneresponsibleforthedisease.

◆Heterochromatin：

chromatinthatstainsdarklythroughoutthecellcycle,evenininterphasegenerallythoughttobelatereplicatingandgeneticallyinactive.SatelliteDNAinregionssuchascentromeres,acrocentricshortarms,and1qh,9qh,16qh,andYqhconstitutesconstitutivehetertochromatin,whereasthechromatinofinactiveXchromosomeisreferredtoasfacultativeheterochromatin.

◆AntisensestrandofDNA:

thenon-codingDNAstrand,whichiscomplementarytomRNAandservesasthetemplateforRNAsynthesis.Alsocalledthetranscribedstrand.

◆Association:

ingeneticepidemiology,describesthesituationinwhichaparticularalleleisfoundeithersignificantlymoreorsignificantlylessfrequentlyinagroupofaffectedindividualsthanwouldbeexpectedfromthefrequencyofalleleinthegeneralpopulationfromwhichtheaffectedindividualsweredrawn.

◆Autosome:

anynuclearchromosomeotherthanthesexchromosomes;22pairsinthehumankaryotype.AdiseasecausedbymutationinanAutosomegeneorgenepairshowsautosomalinheritance.

◆Balancedpolymorphism:

apolymorphismmaintainedinthepopulationbyheterozygoteadvantage,allowinganallele,evenonethatisdeleteriousinthehomozygousstate,topersistatarelativelyhighfrequencyinthepopulation.

◆Carrier:

anindividualheterozygousforaparticularmutantallele.Thetermisusedforheterozygoteforautosomalrecessivealleles,forfemalesheterozygousforX-linkedalleles,or,lesscommonly,foranindividualheterozygousforanautosomaldominantallelebutnotexpressingit（e.g.aheterozygoteforaHuntingtondiseasealleleinthepre-symptomaticstage）.

◆Centromere:

theprimaryconstrictiononthechromosome,aregionatwhichthesisterchromatidsareheldtogetherandatwhichthekinetochoreisformed.Requiredfornormalsegregationinmitosisandmeiosis.

◆Chorionicvillussampling（CVS）:

绒毛细胞取样

◆Chromatin:

thecomplexofDNAandproteinsofwhichchromosomesarecomposed.

◆Chromosomepaintingprobe:

amulti-locusprobedesignedforfluorescenceinsituhybridization（FISH）thathybridizestoonlyoneparticularchromosomeorchromosomearm.（染色体涂染探针：

用于荧光原位杂交的多基因座探针）

◆Dominantnegative:

adisease-causingallele,ortheeffectofsuchanallele,thatdisruptsthefunctionofawild-typealleleinthesamecell.

◆Euchromatin：

themajorcomponentofchromatin,itstainslightlywithGbanding,decondensingandbecominglight-staininginterphase.

◆Expressivity:

theextenttowhichageneticdefectisexpressed.Ifthereisvariableexpressivity,thetraitmayvaryinexpressionfrommildtoseverebutisnevercompletelyunexpressedinindividualswhohavethecorrespondinggenotype.

◆Penetrance：

thefractionofindividualswithagenotypeknowntocauseadiseasewhohaveanysignsorsymptomsofthedisease.

◆Foundereffect:

ahighfrequencyofamutantalleleinapopulationfoundedbyasmallancestralgroupwhenoneormoreofthefounderswasacarrierofthemutantallele.

◆Frameshiftmutation:

amutationinvolvingadeletionorinsertionthatisnotanexactmultipleoftreebasepairsandthuschangesthereadingframeofthegenedownstreamofthemutation.

◆Gatekeepergene:

tumor-suppressorgenesthatdirectlyregulatecellproliferation.看门基因

◆Housekeepinggenes:

genesexpressedinmostorallcellsbecausetheirproductsprovidesbasicfunctions.持家基因

◆Genepool:

alltheallelespresentatagivenlocus

◆Geneticdrift:

randomfluctuationofallelefrequenciesinsmallpopulations.

◆Geneticmap:

therelativepositionsofthegenesonthechromosomes,asshownbylinkageanalysis.

◆Genome:

thecompleteDNAsequence,containingtheentiregeneticinformation,ofagamete,anindividual,apopulation,oraspecies.

◆Imprinting:

thephenomenonofdifferentexpressionofallelesdependingontheparentoforigin.

◆Inbornerrorofmetabolism:

ageneticallydeterminedbiochemicaldisorderinwhichaspecificproteindefectproducesametabolicblockthatmayhavepathologicalconsequences.

◆Karyotype:

thechromosomeconstitutionofanindividual.thetermisalsousedforaphotomicrographofthechromosomesofanindividualsystematicallyarrangedandfortheprocessofpreparingsuchaphotomicrograph.

◆Linkagedisequilibrium:

theoccurrenceofspecificcombinationsofallelesincouplingphaseattwoormorelinkedlocimorefrequentlythanexpectedbychancefromthefrequencyoftheallelesinthepopulation.

◆Lossofheterozygosity:

LOHlossofnormalallelefromaregionofonechromosomeofapair,allowingadefectivealleleonthehomologouschromosometobeclinicallymanifest.Afeatureofmanycausesofretinoblastoma,breastcancerandothertumorsduetomutationinatumor-suppressorgene.

◆Manifestingheterozygote

◆Mitochondrialbottleneck:

astepinoogenesisinwhichonlyasmallsampleofthetotalnumberofmitochondriainanoocyteprecursorispassedontodaughtercells,therebyallowingsignificantvariationintheproportionsofmutantandwild-typemitochondrialinheritedbythedaughtercells.

◆Chimera异源嵌合体Mosaic同源嵌合体

◆Nonsensemutation：

asingle-basesubstitutioninDNAresultinginachain-terminationcodon.

◆Oncogene:

adominantlyactinggeneresponsiblefortumordevelopment.Mutation,over-expression,oramplificationofoncogenesinsomaticcellsmayleadtoneoplastictransformation.Contrastwithproto-oncogeneandwithtumor-suppressorgene.

◆Pedigree:

inmedicalgenetics,afamilyhistoryofahereditarycondition,oradiagramofafamilyhistoryindicatingthefamilymembers,theirrelationshipstotheproband,andtheirstatuswithrespecttoaparticularhereditarycondition.

◆Philadelphiachromosome（Ph）:

thestructurallyabnormalchromosome22thattypicallyoccursinaproportionofthebonemarrowcellsinmostpatientswithchronicmyelogenousleukemia.Theabnormalityisareciprocaltranslocationbetweenthedistalportionof22qandthedistalportionof9q.

◆Pleiotropy：

multiplephenotypiceffectsofasinglealleleorpairofallels.

◆Proband：

theaffectedfamilymemberthroughwhomthefamilyisascertained.

◆Quantitativetrait:

ameasurablequantitythatdiffersamongdifferentindividuals,oftenfollowinganormaldistributioninthepopulation.

◆RFLP:

apolymorphismdifferenceinDNAsequencebetweenindividualsthatcanberecognizedbyrestrictionendonucleases.

◆STRP:

短串联重复序列多态性apolymorphiclocusconsistingofavariablenumberoftandemlyrepeatedbinucleotide,trinucleotideortetranucleotideunitssuchas（TG）n,（CAA）n,（GATA）n;又称微卫星标记

◆SNP:

singlenucleotidepolymorphism:

apolymorphisminDNAsequenceconsistingofvariationinasinglebase.

◆VNTR（可变数目串联重复序列）:

atypeofDNApolymorphismcreatedbyatandemarrangementofmultiplecopiesofshortDNAsequences.Highlypolymorphic,usedinlinkagestudiesandDNA“fingerprinting”forpaternitytestingandforensicmedicine.

◆TagSNPs:

aselect,minimalsubsetofalltheSNPsinagenomicregion,chosenbecausetheyareinlinkagedisequilibriumwithoneanotherinthepopulation.TagSNPsareusefulbecausetheyformaminimumsetofSNPswhoseallelesconstitutehaplotypescapableofrepresentingallthecommonhaplotypesinthatregion.

◆Telomere:

theendofeachchromosomearm.Humantelomeresendwithtandemcopiesofthesequence（TTAGGG）n,whichisrequiredfortheproperreplicationofchromosomeend.

◆Tumor-suppressorgene:

anormalgeneinvolvedintheregulationofcellproliferation.Recessivemutationcanleadtotumordevelopment,asintheretinoblastomageneorthep53gene.Contrastwithoncogene.

基因诊断（间接分析）

单核苷突变的检测：

限制性内切酶谱分析

ASO

ASA（allele-specificamplification）

PCR-SSCP（PCR-singlestrandconformationpolymorphismanalysis）PCR-单链构象多态性分析

变性梯度凝胶电泳（denaturinggradientgeleletrophoresis,DGGE）（A-T丰富的部位DNA双链容易分开，其中错配碱基更易分开）

熔点曲线分析（meltingcurveanalysis）

直接DNA测序