上海交通大学遗传学课件lecture1.

GeneticsYuepingCAOPlantScience一.受精的过程(一)胚珠的结构珠孔珠被卵细胞极核子房壁果皮和种子分别由子房的哪部分发育而来?子房2n子房壁胚珠果皮2n种子果实种子的这些结构又是由胚珠的哪些部位发育而成的?胚珠珠被受精卵受精极核种皮2n胚2n胚乳3n种子Mitosis(有丝分裂)andMeiosis（减数分裂）-Thetransmissionandsegregationofgenesisdeterminedbythemovementofchromosomesthroughmitosisandmeiosis.基因的传递和分离决定于染色体在有丝分裂和减数分裂中的行为-Mitosisandmeiosisonlyoccurineukaryotes,notpresentinprokaryotes.有丝分裂和减数分裂只发生在真核生物ProkaryoticcellsEukaryoticcellsTaxonomicgroupBacteriaAllplants,fungi,animals,Protists（原生生物）Sizetypically5mtypically5mNucleusnotruenuclearmembranenuclearmembraneGeneticmaterialOnecircularmoleculeofDNA,littleproteinLinearmoleculeofDNAandproteinMitosisandmeiosisAbsentPresentDifferencesbetweenprokaryoticandeukaryoticcells.真核细胞和原核细胞的区别Eukaryoticcellsareoftwotypes:Somaticcells-Anycellinahigherorganismthatisnotareproductivecell.2ndesignatesthesomaticchromosomecomplement.在高等生物中，除了生殖细胞以外的任何细胞都是体细胞。Examples:cellsintheskin,musclecells,cellsinroots.Gameticcells-Reproductivecells.Gameticcellshave1/2thechromosomecomplementofsomaticcells.Examples:Plants–eggandpollencellsAnimals-eggandspermcells.Examplesofthenumberofchromosomeinvariousspecies-Mostanimalsomaticcellsare_Diploid____.Diploidcellshave_2_setsofchromosomes.Mostanimalgameticcellsare_Haploid_.Haploidcellshave_1_setofchromosomes.-Plantspeciesvaryinthenumberofsetsofchromosomes.Forexample,wheatisa_Hexaploid__with_6_setsofchromsomes.No.ofchromosomesSpecies2nnHumans4623Maize2010Dog7839Indianfern1260630Australianant21Homologouschromosome（同源染色体）Chromosomes-Duringmitosisandmeiosis,stainedchromosomesarevisiblewithalightmicroscope.在有丝分裂列和减数分裂过程中在光学显微镜下可以看到染色体。-Whatarechromosomescomposedof?染色体的组成是:DNA,proteinandRNAHomologouschromosomes——-apair(indiploids)ofessentiallyidenticalchromosomesthatjoinandrecombineDNAinmeiosis.同源染色体是是在减数分裂中可以重新结合在一起的大小形态相同的染色体（体条来自父本，一条来自母本）。-Humanshave23pairsofhomologouschromosomes.-Chromosomescanbeclassifiedbasedonsizeandpositionofcentromere.-Homologouschromosomesarethesamesizewiththeexceptionofthesexchromosomes.Homologouschromosomes-Chromosomescanbeclassifiedbasedonsizeandpositionofcentromere.-Homologouschromosomesarethesamesizewiththeexceptionofthesexchromosomes.Beloware2homologouschromosomes.Oneofthesechromosomeswouldbefromthisindividual’smotherandtheotherfromthefather.Eachhomologouschromosomeconsistsoftwochromatids.Thetwochromatidonachromosomecontainidenticalgeneticinformation.ThisinformationwasrecentlyreplicatedduringtheSphaseofthecellcycle.Thetwohomologouschromosomeswouldcarryalternativeallelesforgenes.Forexample,iftheindividualisheterozygousAa,onehomologouschromosomewouldcarrytheAalleleandtheotherchromosomewouldcarrytheaallele.Becausetwochromatidsonthesamechromosomecarryidenticalgeneticinformation,bothchromatid1and2wouldcarrytheAalleleandchromatids3and4wouldcarrytheaallele.Humanshave23pairsofhomologouschromosomesChromatid2Chromatid3Chromatid4Chromatid1Chromatid1HomologouschromosomesofhumanMitosis（有丝分裂）Mitosis-Nucleardivisionwitheachdaughtercellsreceivinganidenticalcomplementofchromosomes.有丝分裂---核分裂每个子细胞得到一套完整相同的染色体-Mitosisisonlyapartofthecellcycle.有丝分裂仅仅是细胞周期的一部分Mitosis（有丝分裂）Mitosisisabout10%ofthetimeofthecellcycle.Thisiswhencelldivisionoccurs.DuringG1,metabolicactivityoccursandthisstagetakesabout25%ofthetimeofthecellcycle.DuringtheSstage,DNAreplicationoccursandthistakesabout40%ofthecellcycletime.MetabolicactivityoccursduringG2andthisstagetakestheremaining25%ofthecellcycle.Rapidlydividingeukaryoticcellscangothroughtheentirecyclein16hours.Synthesisstage(S)G1stageMitosisG2stageCellCycleStagesofMitosis（有丝分裂的时期）Mitosisisacontinuousprocessbutitcanbedividedintofourstages（有丝分裂是一个连续的过程，分4个时期）.1.Prophase（前期）–Chromosomescondense,nuclearmembranedisintegrates.2.Metaphase（中期）-Mitoticspindleforms,chromosomesbecomeattachedtothespindleandthechromosomeslineupatthecentralplane.3.Anaphase（后期）-Chromosomesdividelongitudinally.Onesisterchromatidmovestoeachpole.4.Telophase（末期）-Nuclearmembranereforms,celldivisionoccurs.StagesofMitosis---InterphaseInterphase(间期)StagesofMitosis----prophaseProphase（前期）.–Chromosomescondense,nuclearmembranedisintegrates.StagesofMitosis----MetaphasecentromereMetephase（中期）Mitoticspindleforms,chromosomesbecomeattachedtothespindleandthechromosomeslineupatthecentralplaneStagesofMitosis----AnaphaseAnaphase（后期）-Chromosomesdividelongitudinally.Onesisterchromatidmovestoeachpole.StagesofMitosis----TelophaseTelophase（末期）-Nuclearmembranereforms,celldivisionoccursMeiosis（减数分裂）Meiosis-Theprocessingametogenesisorsporogenesisduringwhichonereplicationofthechromosomesisfollowedbytwonucleardivisionstoproducefourhaploidcells.减数分裂--在配子体形成过程中，染色体复制1次进行2次核分裂，形成4个单倍体细胞。StagesofMeiosis（减数分裂的时期）ProphaseI-Chromosomescondenseandpair,crossingoverbetweenhomologouschromosomesoccurs（染色体浓缩，同源染色体配对，交换）.MetaphaseI-Homologouschromosomeslineupatthemetaphaseplane.Theorientationofthechromosomesisrandom.同源染色体排列在赤道板两侧，染色体的朝向（被分配到哪极）是随机的AnaphaseI-Homologouschromosomesseparate.Thisisreferredtoasareductionaldivision.同源染色体分离，即所说的减数分裂。TelophaseI-Cellsdivide.细胞分裂。ThereisnochromosomereplicationbetweenmeiosisI