基因工程Chapter 2Word下载.docx
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基因工程Chapter 2Word下载.docx
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Itisanewscienceinbiologicaltechnologysetupin1970`sbasedonthecomprehensiveprogressofmolecularbiologyandmoleculargenetics
1ststage:
Before50`s.chromosome
2ndstage:
after50`s~80`s,largemolecular__molecularbiology
3ndstage:
from80`s__genefunction__phenotyperelationship_Reversebiology(R_genetics)
1基因学说的创立StepupofGenetheory
2基因与DNA分子GeneandDNAmolecular
①Whatisgene?
②1953Watson—Crickdoublehelixmodel.
EveryorganismpossessesagenomethatcontainsthebiologicalinformationneededtoconstructandmaintainalivingexampleofthatorganismMostgenomesincludingthoseforallcellularlifeforms,aremadeofDNA(Deoxyribonucleicacid),butafewviruseshaveRNA(Ribonucleicacid)genomes.DNAandRNAarepolymericmoleculesmadeupoflinear,unbranchedchainsofmonomericsubunitscallednucleotides.Eachnucleotidehasthreesparts:
asugaraphosphategroupandabase.InDNA,thesugaris2`_deoxyriboseandthebasesareadenine(A),cytosine(C),guanine(G),andthymine(T).
NucleotidesarelinkedtooneanotherbyphosphodiesterbondstoformaDNApolymer,,orpolynucleotide.Whichmightbeseveralmillionnucleotidesinlength,DNAinlivingcellsisdouble—strand,twopolynucleotidesbeingwoundaroundareanothertoformthedoublehelix.Thedoublehelixisheldtogetherbyhydrogenbondsbetweenthebasecomponentsoftheneucleotidesinthetwostrands.Thebase-pairingrulesarethatAbase-pairswithT,andGbase-pairswithC.ThetwoDnamoleculesinadoublehelixthereforehavecomplementarysequences.
InanRNAnucleotidethesugarisriboseratherthem2`-deoxyribose,andthymineisreplacedbytherelatedbaseuracil(U).RNApolymersarerarelymorethemafewthousandnucleotidesinlength,andRNAinthecellisusuallysingle-stranded,althoughbasepairsmightform,betweendifferentpartsofasinglemolecule.
ThebiologicalinformationcontainedinagenomeisencodedinthenucleotidesequenceofitsDNAorRNAmoleculesandisdividedintodiscreteunitscalledgenes.Theinformationcontainedinageneisreadbyproteinsthatattachtothegenomes,thisprocesswasoriginallylookedonascomprisingtwostages,transcriptionandthesecondresultinginsynthesisofaproteinwhoseaminoacidsequenceisdetermined,viathegeneticcode,bythenucleotidesequenceoftheRNAtranscript
ThegenomeistheentireDNAcontentofacell,includingallofthegenesandalloftheintergenicregions.Acompletecopyofthegenomemustbemadeeverytimeacelldivides.DNAreplicationhastobeextremelyaccurateinordertoavoidtheintroductionofmutationsintothegenomecopiesSomemutationsdo,however,occur,eitheraserrorsinreplicationorduetotheeffectsofchemicalandphysicalmutagenethatdirectlyalterthechemicalstructureofDNA,DNArepairenzymescorrectmanyoftheseerrors;
thosethatescapetherepairprocessesbecomepermanentfeaturesofthelineagedescendingfromtheoriginalmutatedgenome.Theseevents,alongwithgenomerearrangementsresultingfromrecombinationunderliemolecularevolution,thedivingforcebehindtheevolutionoflivingorganisms.
Thehumangenomecontainsapproximately80000genes,butthecodingregionofthesegenestakeuponly3%thegenome.
Theyeastgenomecontains6000genesandhasamorecompactorganization.
ThegenomesofsomeplantsaredominatedbyrepetitiveDNAsequence.
Althoughthebasicphysicalstructuresofalleukaryoticnucleargenomesaresimilar,oneimportantfeatureisverydifferentorganisms.Thisisgenomesize,thesmallesteukaryoticgenomesbeinglessthem10Mbinlength,andthelargestover100000Mb.
③Genomesizesofsomeorganisms
Organism
Genomesize(Mb)
Prokaryote
Mycoplasmagenitalium
0.58
Escherichiacoli
4.64
Bacillusmegaterium
30
Eukaryote
Fungi
Saccharomycescerevisiae(yeast)
12.1
Aspergillusnidulans
25.4
Magnaporthegrisea
38.8
Protozoa(原生动物)
Tetrahymenapyriformis
190
Invertebrates(无脊椎动物)
Caenorhabditiselegans(Nematodeworm)
100
Drosophilametanogoaster(fruitfly)
140
Bombyxmon(silkworm)
490
Strongylocentrotuspurpuratus(seaurchin海胆)
845
Locustamigratoria(locust)
5000
Vertebrate
Fugurubripes(pufferfish)
400
Homosapiens(human)
3000
Musmusculus(mouse)
3300
Plant
Arabidopsisthaliana(vetch)
Oryzasativa(rice)
565
Pisumsativum(pea)
4800
Zeamays(maize)
Triticumaestivum(wheat)
17000
Fritillariaassyriaca(fritillary贝母)
120000
3基因与DNA的多核苷酸区段
GeneandpolynucleotidefragmentofDNA
传统的基因概念:
基因是成串地在DNA分子上一个接一个地排列着,它们之间由非遗传物质连接起来,交换在基因
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