CelldifferentiationandCancercellsThedifferentcelltypesofamulticellularorganismcontainthesameDNA.Acellcanchangetheexpressionofitsgenesinresponsetoexternalsignals.DifferencesinmRNAexpressionpatternsamongdifferentcelltypes.Differentcelltypessynthesizedifferentsetsofproteins.GeneexpressioncanberegulatedatmanyofthestepsinthepathwayfromDNAtoRNAtoprotein.Thefouressentialprocessesbywhichamulticellularorganismismade:Cellproliferation,Cellspecialization,Cellinteraction,andCellmovement.Celldifferentiationoccursinmulticellularorganisms2.Whyafertilizedeggcandevelopintodifferentcells:Genedifferentiatedexpress3.CombinationalcontrolandGenedifferentiatedexpresspp.416:12-1:2n(n=3,A,B,C)4.House-keepinggenesandluxurygenes5.Transdifferentiation:FromonetypeofcellintoanothertypeCelltotipotency(细胞全能性)2.Animalcloning—Dolly:Alambwithnofather克隆能给人类带来什么？Stemcellanditsdifferentiationpotential2.Wheretogetthestemcells?(2)Adultstemcells(3)Umbilicalcordbloodstemcells3.Typesofstemcells:differentiationpotential(2)Pluripotentstemcells(3)EmbryonicstemcellsTwowaysforastemcelltoproducedaughterswithdifferentfates4.Whydoresearchersstudystemcells?5.StemcellplasticityProductionofdifferentiatedcellsfrommouseEScellsinculture.Stemcellsmigratetositesoforgandamageanddifferentiatetocelltypescompetenttoparticipateintissueregeneration.RegenerationofnewtissuesfromourowncellswillnotbefarbehindScience,December6,2002:1901Cancer:CellsproliferateuncontrollablyBenigntumor1.Thebiologycharacteristicsofcancer(3)Lesswelldifferentiatedthannormalcellsorbenigntumorcells(5)LoseContactinhibitioninvitro2.Thecausesofcancer3.Caner:Asaresultoftheaccumulationofmutationandnaturalselection癌基因（oncogenes）：v-oncandc-onc抑癌基因（tumor-suppressorgene）Rbp53特点原癌基因抑癌基因基因属性细胞增殖必需细胞分化必需致癌方式基因突变激活、异常表达基因缺失或失活1976年发现，正常鸡细胞核DNA中，具有与V-onc的同源序列，称正常细胞中的同源序列为原癌基因（protooncogene）,或C-oncogene.v-onc和c-onc的关系：c-onc来自v-onc.理由如下:1、v-onc对病毒复制和生存都是不必要的；而c-onc对细胞重要功能和活动不可缺少；提示c-onc是进化中保存下来的细胞重要结构元件。2、发现的30种c-onc是依靠病毒的v-onc探针找到的；并不是所有c-onc都有对应的同源