生物化學(xué)課件 4 Information pathway-genes and chromosomes

InformationPathwayThecentraldogma(中心法則)ofmolecularbiology23ThecentraldogmaofmolecularbiologyDNA是自身復(fù)制的模板。DNA通過轉(zhuǎn)錄作用將遺傳信息傳遞給中間物質(zhì)RNA。RNA通過翻譯作用將遺傳信息表達(dá)成蛋白質(zhì)。

中心法則揭示了遺傳信息的傳遞方向，反映了DNA、RNA和蛋白質(zhì)之間的相互關(guān)系。4ContentsGenesandchromosomesDNAmetabolismRNAmetabolismProteinmetabolismRegulationofgeneexpressionRecombinantDNAtechnology5GenesandchromosomesChromosomalelementsThesizeandsequencestructureofDNAmoleculesDNAsupercoilingChromatinstructure61.Chromosomalelements7WhatareGenes?AportionofachromosomethatdeterminesoraffectsasinglecharacterofphenotypeOnegene-oneenzymeOnegene-oneproteinOnegene-onepolypeptideGenesaresegmentsofDNAthatcodeforpolypeptidechainsandRNAs8ChromosomesDNAmoleculesarethelargestmacromoleculesinthecellandarecommonlypackagedintostructurescalledchromosomes.Chromosome:asinglelargeDNAmoleculeanditsassociatedproteins,containingmanygenes;storesandtransmitsgeneticinformation.9GenomeTogether,allofacell`sgenesandintergenicDNA(theDNAbetweengenes)formthecellulargenome.Genome:Allthegeneticinformationencodedinacellorvirus.10Eukaryoticchromosomesareverycomplex10%highlyrepetitive(alsocalledsimple-sequenceDNA,satelliteDNA) Less10bp,repeatedmillionsoftimes20%moderatelyrepetitive Afewhundredbp,repeated1000times1112Splitgenes(斷裂基因)Interveningsequences:introns(內(nèi)含子)thenontranslatedDNAsegmentsingenesExons（外顯子）

Thecodingsegments13142.ThesizeandsequencestructureofDNAmolecules151,7mmand2um1617BacteriacontainchromosomesandextrachromosomalDNAPlasmids Small,circular,freeinthecytosol,extrachromosomalDNA18DNAfromalysedE.colicell19Orgenelles（細(xì)胞器）

ofeukaryoticcellsalsocontainDNAMitochondrialDNA(mtDNA) Circularduplex,lessthan20kbinanimalcells,200-2500kbinplantcellsChloroplastDNA(cpDNA) Circularduplex,120kb-160kb Evolutionaryorigin?203.DNAsupercoiling212223RelaxedandsupercoiledDNAs244.ChromatinstructureChromosome（染色體）andchromatin（染色質(zhì)）25Nucleosomes(核小體)

arethefundamentalorganizationalu