基因工程Chapter 2.docx

基因工程Chapter 2.docx

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基因工程Chapter2

基因工程原理

TheprinciplesofGeneengineering

Chapter1Gene&Geneengineering

§1.DevelopmentofGenestudy

Whatisgeneengineering?

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

Organism

Genomesize（Mb）

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

Organism

Genomesize（Mb）

Vertebrate

Fugurubripes（pufferfish）

400

Homosapiens（human）

3000

Musmusculus（mouse）

3300

Organism

Genomesize（Mb）

Plant

Arabidopsisthaliana（vetch）

100

Oryzasativa（rice）

565

Pisumsativum（pea）

4800

Zeamays（maize）

5000

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