细胞生物学第十章 细胞核（二）.ppt

Chapter10NucleiandChromosomes细胞核和染色体-2,MedicalCellBiology,JingChangqin(井长勤)associateprofessorE-mail：jingchangqin,2,2.2.2Twoclassesofheterochromatin,ConstitutiveHeterochromatin:Compactedstateatalltime:CentromereFacultativeHeterochromatin:InactivatedatcertainphaseoflifeXchromosomeinactivation(barrbody),3,2.3Componentofchromatin,DNA,protein,RNA,histone：H1、H2A、H2B、H3、H4,nonhistone,4,2.3.1DNAofchromatin,Geneticmaterialinmostcells46DNAmoleculesinahumancell,EachDNAmoleculeformsalinearchromosome3109bp/genomeThecomplexityofeukaryoticgenomesGenomesizegenerallyincreaseswithanorganismscomplexity.Nocodingsequenceandrepeatingsequence,5,2.3.1.1NonrepeatedDNA,Protein-codingsequences25-50%oftheprotein-codinggenesaresolitarygenes.Othersbelongtogenefamily,whichencodeproteinswithsimilarbutnonidenticalaminoacidsequences.-likeglobingenefamily:Contains5functionalgenes,6,2.3.1.2ModeratelyrepeatedDNA,TandemlyrepeatedgenesencoderRNAs,tRNAs,andHistones5SrRNAandpre-rRNAgenes:Morethan100copy/Genome.Thesegenesareneededtomeetthegreatcellulardemandfortheirtranscripts,7,2.3.1.3HighlyrepeatedDNA,Simple-sequence,NoncodingDNASatelliteDNA:Centromeres,Telomeres(105107bp)MicrosatelliteDNA:102105bpateachsiteMinisatelliteDNA:10100bpateachsite,8,HistoneFiveclasses:H1,H2A,H2B,H3,H4Highquantityhistone:DNA1:1ThemostabundantproteinsassociatedwitheukaryoticDNA,2.3.2Proteinofchromatin,9,Richinpositivelychargedbasicaminoacids,whichinteractwiththenegtivelychargedphosphategroupsinDNATheaminoacidsequencesofhistonesH2A,H2B,H3,H4areremarkablysimilaramongdistantlyspecies,2.3.2Proteinofchromatin,10,NonhistoneIncludealargenumberofwidelydiversestructuralenzymatic,andregulatoryproteinsMostofwhichhavetobecharacterized,2.3.2Proteinofchromatin,11,2.4Organizationofchromatin,FourlevelsoforganizationofchromatinNucleosome(10nmindiameter)30nmfiberLoopeddomainsMetaphasechromosome,12,2.4.1nucleosome,Thebasicunitofchromatinthelowestlevelofchromatinorganization10nmorsoThepackingratiooftheDNAofnucleosomesisapproximately7:1.,13,2.4.1Thestructureofnucleosome,Histonecore,DNA(140-160bp、1.75圈）,H2A,H2A,H2B,H2B,LinkerDNA（50-60bp）,nucleosome,Coreparticle,Linkingpart,DNA：140-160bp、1.75loop,histone：2（H2A、H2B、H3、H4）,histone：H1,DNA：5060bp,14,2.4.230nmfiber,Thenucleosomalfilamentiscoiledintothehigher-order,thickerfiber(30nmfiber)ThesecondlevelofchromatinorganizationTheDNA-packingratiois6-fold.,15,2.4.3Loopeddomains,The30nmchromatinfiberisgatheredintoaseriesoflarge,supercoiledloops,ordomains.ThethirdlevelofchromatinorganizationThelengthofDNAisfurthershortenedtoonefortieth(1/40).,16,2.4.4Metaphasechromosome,Themitoticchromosomerepresentstheultimateinchromatincompactness.Thepackingratio5:1,17,Inall,DNAispactedto1/10000inlength,18,Characteristicsofactivechromatin,activechromatinandinactivechromatinDNasehypersensitivesite（超敏感位点）particularityinbiochemistry（生化上具有特殊性）LittlecombinationwithhistoneH1HighlyacetylatedhistonelittlephosphorylatedhistoneH2BRarelyvariatedhistoneH2AHMG14+17onlyexistinactivechromatin,19,2.5summary,NatureofchromatinTwotypesComponentsOrganization,20,Exercise,1.Explainthekeywordsnucleosome.2.Tellthedifferenceshistoneandnon-histone.3.Thestructureofnucleosome.,21,1.翟中和等主编.细胞生物学，第3版,高等教育出版社，20072.韩贻仁主编.分子细胞生物学(第3版),高等教育出版社,20073.艾伯茨等著，赵寿元等译.基础细胞生物学，上海科学技术出版社，20024.王金发.细胞生物学,科学出版社，20045.杨恬.细胞生