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1、6.1GeneandChromosomes6.2Functionalstructureofagene6.3GeneExpression6.4EssentialsforGeneticEngineering–AdditionalReadingChapter6MolecularGeneticsGeneAgeneisaunitofheredityinalivingorganism.ItisanamegiventosomestretchesofDNAandRNAthatcodeforatypeofproteino
2、rforanRNAchainthathasafunctionintheorganism.Livingthingsdependongenes,astheyspecifyallproteinsandfunctionalRNAchains.Genesholdtheinformationtobuildandmaintainanorganism'scellsandpassgenetictraitstooffspring,althoughsomeorganelles(e.g.mitochondria)areself
3、-replicatingandarenotcodedforbytheorganism'sDNA.Allorganismshavemanygenescorrespondingtomanydifferentbiologicaltraits,someofwhichareimmediatelyvisible,suchaseyecolorornumberoflimbs,andsomeofwhicharenot,suchasbloodtypeorincreasedriskforspecificdiseases,or
4、thethousandsofbasicbiochemicalprocessesthatcompriselife.6.1GeneandChromosomesAmodernworkingdefinitionofageneis"alocatableregionofgenomicsequence,correspondingtoaunitofinheritance,whichisassociatedwithregulatoryregions,transcribedregions,andorotherfunctio
5、nalsequenceregions".Colloquialusageofthetermgene(e.g."goodgenes","haircolorgene")mayactuallyrefertoanallele:ageneisthebasicinstruction,asequenceofnucleicacids(DNAor,inthecaseofcertainvirusesRNA),whileanalleleisonevariantofthatgene.Thus,whenthemainstreamp
6、ressrefersto"having"a"gene"foraspecifictrait,thisisgenerallyinaccurate.Inmostcases,allpeoplewouldhaveageneforthetraitinquestion,butcertainpeoplewillhaveaspecificalleleofthatgene,whichresultsinthetraitvariant.Inthesimplestcase,thephenotypicvariationobserv
7、edmaybecausedbyasingleletterofthegeneticcode-asinglenucleotidepolymorphism.6.1GeneandChromosomes(Continued)ProfessionalWordsandPhrasesheredity[hi'rediti]n.遗传genetictrait遗传性状mitochondria[maitə'kɔndriə]n.线粒体mitochondrium的复数形式biologicaltrait生物性状inheritance[
8、in'heritəns]n.遗传，继承物allele[ə'li:l]n.等位基因variant['veriənt]n.变体，变型phenotypic['fi:nətipik]adj.表型的variation[veri'eiʃən]n.变种，变化polymorphism[pɔli'mɔ:fizəm]n.多态性ChromosomesThetotalcomplementofgenesinanorganismorcellisknownasitsge
