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1、专题一：QTL及其定位方法QTL的概念QTL检测方法用于QTL定位的群体统计方法图距函数QTL检测所需标记数预估QTL的概念1、AQTLisasegmentofchromosomeaffectingthetrait,notnecessarilyasinglelocus--D.S.Falconeretal,19952、Aquantitativetraitloci(QTL)isdefinedasasinglegeneoraclusterofcloselylinkedgenesthathavealarge
2、effectonaquantitativetrait.--P.Sorensen,2000QTL的概念3、QTL,quantitativetraitlocus,isaplace(region)thataffectstraitinthegenome.Itcouldspanseveralgenes,oneormoreofwhichaffectsthetrait,butithasbecomecommontotake'QTL'asequalto'majorgene'.——B.Kinghorn,2000理解：一
3、个QTL指在基因组中占据一定染色体区域，控制同一性状的一组微效多基因的集合（基因簇）或单个基因。但目前的研究中大部分将QTL理解为单个基因（或主效基因）。一个数量性状可能受多个QTL影响；一个QTL也可能影响多个数量性状。QTL的概念QTL的特点（与传统的孟德尔因子比较）结构更松散，一个QTL内各微效基因间可能有比孟德尔因子内高得多的重组率，因此一个QTL并不象一个孟德尔位点那样独立分离和有明显的性状效应。QTL的概念QTL概念提出的意义（D.S.Falconer--1995）1、Itcouldim
4、provetheefficacyofselectivebreeding,especiallyfortraitswithlowheritabilityorthatcanonlybemeasuredinonesex.2、Transgenictechnologymightbeappliedtoquantitativetraits.QTL的概念3、Inmedicine,theidentificationofallelescausingpredispositiontocommonmultifactoriald
5、iseasescouldleadtoimprovedmethodsofprevention.4、Quantitativegenetictheorywillbemademorerealisticwhenthenumbersandpropertiesofthegenesareknown,andthemorerealistictheorieswillimproveourunderstandingofevolution(and/orthedevelopmentofthequantitativetraits)
6、.QTL检测方法Candidategeneapproach(Hayes,2007)Thecandidategeneapproachassumesthatageneinvolvedinthephysiologyofthetraitcouldharbouramutationcausingvariationinthattrait.Thegene,orpartsofthegene,aresequencedinanumberofdifferentanimals,andanyvariationsintheDNA
7、sequences,thatarefound,aretestedforassociationwithvariationinthephenotypictrait.CandidategeneapproachTherearetwoproblemswiththecandidategeneapproach:Firstly,thereareusuallyalargenumberofcandidategenesaffectingatrait,somanygenesmustbesequencedinseverala
8、nimalsandmanyassociationstudiescarriedoutinalargesampleofanimals.Secondly,thecausativemutationmaylieinagenethatwouldnothavebeenregardedaprioriasanobviouscandidateforthisparticulartrait.QTL检测方法侯选基因途径的原理与方法：1、选定侯选基因：根据现有的生物学、生理、生化知识，对数量性状
