分子生物学（双语）6GenomeSequencesandGeneNumbers

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1、Chapter6GenomeSequencesandGeneNumbers6.1IntroductionFIGURE01:TheminimumgenenumberrequiredforanytypeoforganismincreaseswithitscomplexityPhotoofintracellularbacteriumcourtesyofGregoryP.HendersonandGrantJ.Jensen,CaliforniaInstituteofTechnologyPhotooffree-livin

2、gbacteriumcourtesyofKarlO.Stetter,UniversitätRegensburgPhotoofunicellulareukaryotecourtesyofEishiNoguchi,DrexelUniversityCollegeofMedicinePhotoofmulticellulareukaryotecourtesyofCarolynB.MarksandDavidH.Hall,AlbertEinsteinCollegeofMedicine,Bronx,NYFIGURE01:The

3、minimumgenenumberrequiredforanytypeoforganismincreaseswithitscomplexity6.1IntroductionPhotoofhigherplantcourtesyofKeithWeller/USDAPhotoofmammal©Photodisc6.2ProkaryoticGeneNumbersRangeOveranOrderofMagnitudeTheminimumnumberofgenesforaparasiticprokaryoteisabout

4、500;forafree-livingnonparasiticprokaryoteitisabout1500.FIGURE02:GenomesizesandgenenumbersareknownfromcompletesequencesforseveralorganismsFIGURE03:Thenumberofgenesinbacterialandarchaealgenomesisproportionaltogenomesize6.2ProkaryoticGeneNumbersRangeOveranOrder

5、ofMagnitudepathogenicityislands–DNAsegmentsthatarepresentinpathogenicbacterialgenomesbutabsentintheirnonpathogenicrelatives.horizontaltransfer–ThetransferofDNAfromonecelltoanotherbyaprocessotherthancelldivision,suchasbacterialconjugation.6.3TotalGeneNumberIs

6、KnownforSeveralEukaryotesThereare6000genesinyeast;18,500inaworm;13,600inafly;25,000inthesmallplantArabidopsis;andprobably20,000to25,000inmiceandhumans.FIGURE04:Thenumberofgenesinaeukaryotevariesfrom6000to40,000butdoesnotcorrelatewiththegenomesizeorthecomplex

7、ityoftheorganismFIGURE05:TheS.cerevisiaegenomeof13.5Mbhas6000genes,almostalluninterrupted6.3TotalGeneNumberIsKnownforSeveralEukaryotesmonocistronicmRNA–mRNAthatcodesforonepolypeptide.polycistronicmRNA–mRNAthatincludescodingregionsrepresentingmorethanonegene.

8、6.3TotalGeneNumberIsKnownforSeveralEukaryotesFIGURE06:FunctionsareknownforonlyhalftheflygenesAdaptedfromDrosophila12GenomesConsortium,Nature450(2007):203-218.6.4HowManyDifferentTypesofGenesAreTh