大学分子生物学经典双语课件C2 gene and chromosome.ppt

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1、Chapter2GeneandChromosomeContents1StructureofDNA2Denaturation,renaturationandhybridization4GeneclusterandrepetitivesequenceConceptofgene3Chromosomeandnucleosome5Genome6Geneticinformationflow72.1StructureofDNA2.1.1primarystructureofDNADefinition：thenucletideresiduesequ

2、enceofthepolynucleotidechain；Linkage：3’,5’-phosphodiesterbond；Backbone：phosphate+pentose；Direction：5’→3’；2.1.2secondarystructureofDNA----DNAdoublehelixX~rayphotographofDNAwithhighquality：DNAspecimensfromdifferentspecieshavethesameresults（constantwidth;3.4nm）；Chargaffr

3、ules：theruleofthecompositionofDNAPhysicalchemistrystudiesandacidandalkalititratestudiesonDNAbase；ExperimentalbasisThreedimensionalstructureofDNA10.5bp/turnSugar-Pbackboneisperpendiculartotheplanarbasepairs5’5’3’3’PitchlengthTheWatson-CrickBformDNADeducedbymodelbuildin

4、g11Å20ÅFig8-15chargedPO4--ontheoutsideHydrophobicbasesinsidekeynotesofDNAdoublehelixTwopolynucleotidechainsinaDNAdoublehelix;Alongthesameaxis，twochainsarewoundaroundeachother,resultinginaright-handeddoublehelix;FormsamajorgrooveandaminorgrooveThebaseslieontheinside，th

5、esugar-phosphatebackboneisontheoutside;Thebasesareflatstructure,lyinginpairsperpendiculartotheaxisThediameterofthedoublehelixis2nm;Thereisacompleteturnevery3.4nm,with10bpperturn.2.1.2.1StablefactorsofthedoublehelixBase-stackinginteraction（hydrophobiceffect,themajorfac

6、tor）；Hydrogenbondbetweencomplementarybasepairs；electrovalentbond（betweenthenegativechargescarriedonthephosphategroupsandthepositivechargescarriedontheproteinsormetalions）2.1.2.2ConformationpolymorphismofthedoublehelixAlternativedouble-helicalstructuresofDNABaseObliqui

7、tyhelixriseperbasepairbpnumberperturnHelicalsensediameter（nm）B-formZ-form0-119-2090.34nm0.23nm0.38nm101112RhandedRhandedLhanded2.0-2.372.551.8-1.84A-formB-form：relativehumidityis92%A-form：relativedevoidofwater(under75%)Z-form：lefthandedhelixH-form：triplehelix2.1.3T

8、riplexDNA1953,Watson&CrickproposedD.SDNAmodelandfoundmanyredundanthydrogenbondingdonorandreceptorsalongbiggrooves.1957,Felse