遗传物质的分子基础.ppt

Garrod:Onemutantgene–Onemetabolicblock在20世纪初，英国医生A.Garrod首先发现人类中几种先天性代谢缺陷疾病，如苯丙酮尿症（phenylketonuria简称PKU）就是由一个常染色体隐性基因决定的。BeadleTatum(1941)：“onegeneoneenzyme”用X射线诱导处理红色面包霉，筛选出被诱导的突变体来进行实验。根据遗传分析和大量研究，他们认为基因发生突变，就可能导致酶活性的丧失。基因：arg1arg2arg3酶：E1E2E3前体：前体?鸟氨酸?瓜氨酸?精氨酸研究血红蛋白时发现，正常HbA有四条多肽链（2条?链，2条?链）VernonM.Ingram证明?链第六位氨基酸HbA是谷氨酸，HbS是缬氨酸（镰刀形细胞贫血症）。这是证明基因与氨基酸之间存在直接对应关系的第一个直接证据。OneGene,OneProtein；OneGene,OnePolypeptideChain二、Evolutionoftheconceptofthegene:StructureTheBeads-on-a–stringconceptAccordingtothisbeads-on-a-stringconcept,thegenewasthebasicunitofgeneticinformationdefinedbythreecriteria:(1)function,(2)recombination,and(3)mutation.Theunitoffunction,theunitofgeneticmaterialthatcontrolledtheinheritanceofonecharacteroroneattributeofphenotype.Theunitofstructure,operationallydefinedintwoways:Byrecombination:astheunitofgeneticinformationnotsubdivisiblebyrecombination.Bymutation:astheunitofgeneticmaterialcapableofindependentmutation.㈠、DiscoveryofrecombinationwithinthegeneIn1940,studiedmutationsatthelozengelocusontheXchr.ofDrosophila:alleleslzs“spectacle”eyelzg“glassy”eyefemalelzs/lzglozengexmalelzsorlzg?0.2%wild-typeprogeny?Reversion???1.Thefreq.ofreversionoflzsorlzgtow.t.inhemi-zygouslozengemaleswasmuchlowerthan0.2%;2.Therarew.t.progenyalwayscarriedanXchr.Withlz+thatwasflankedbyrecombinantout-sidermarkers.Theresultsofthesepioneeringstudiesfirstindicatedthatthegenewasmorecomplexthanabeadonastring:thegenewasdivisible,containingsitesthatwereseparablebycrossingover.㈡、基因的微细结构1955年，美国的S.Benz