分子生物學第2章1部分和基因組

Chapter2.Geneand第二 Yu-xiangZhang,PhDDepartmentofBiochemistryandE-mail: Chapter2.Geneand第二 Section1.Section2.GenomeandGenomicsSection3.GenomicPolymorphismSection1.Genesarethebasicphysicalandfunctionalunitsofheredity.Eachgeneislocatedonaparticularregionofachromosomeandhasaspecificorderedsequenceofnucleotides.Centraldogmaofmolecularbiology:DNARNAProteinGeneticinformationisstoredinSegmentsofDNAthatencodeproteinsorotherfunctionalproductsarecalledgenes.GenesequencesaretranscribedintomessengerRNAintermediates(mRNA).mRNAintermediatesaretranslatedintoproteinsthatperformmostlifefunctions.geneTheviralgenomecanconsistofaverysmallnumberofgenesoruptohundredsofgenesdependingonthetypeof Notethatthegenomeistypicallyorganizedasalongmoleculethatisusuallystraightorcircular.es: particle,alsoknownasavirion,isessentiallyanucleicacid(DNAorRNA)enclosedinaproteins orcoat. areextremelysmall,approxima y15-25nanometersindiameter.Splitegene:ExonsvsEukaryoticgeneshaveintronsandexons.Exonscontainnucleotidesthataretranslatedintoaminoacidsofproteins.ExonsareseparatedfromoneanotherbyinterveningsegmentsofjunkDNAcalledintrons.Intronsdonotcodeforprotein.TheyareremovedwheneukaryoticmRNAisprocessed.ExonsmakeupthosesegmentsofmRNAthataresplicedbacktogetheraftertheintronsareremoved;theintron-freemRNAisusedasatemplatetomake3ExonsaresequencesofDNAthat3expressedintoCIntronsareinterveningsequencesthatarenottranslatedintoproteinC1212C312C31212C3123ExonsandWhat’sthedifferencebetweenexonsandExonsoftenaredescribedasshortsegmentsofcodingsequence.Thisisabitofanoversimplification.Exonsarethosesegmentsofsequencethataresplicedtogetheraftertheintronshavebeenremovedfromthepre-mRNA.Yes,thecodingsequenceiscontainedinexons,butitispossibleforsomeexonstocontainnocodingsequence.Portionsofexonsorevenentireexonsmaycontainsequencethatisnottranslatedintoaminoacids.ThesearetheuntranslatedregionsorUTRs.UTRsarefoundupstreamanddownstreamoftheprotein-codingWhatisaAlocusdescribestheregionofachromosomewhereageneislocated.11p15.5isthelocusforthehumaninsulingene.11isthechromosomenumber,pindicatestheshortarmofthechromosome,and15.5isthenumberassignedtoaparticularregiononachromosome.Whenchromosomesarestainedinthelab,lightanddarkbandsappear,andeachbandisnumbered.Thehigherthenumber,thefartherawaythebandisfromtheIntergenicregionandRegulatorySection2.Genomeand組 組 組 Thegenomeistheentiretyofanorganism'shereditaryinformation.ItisencodedeitherinDNAor,formanytypes es,inRNA.Thegenomeincludesboththegenesandthenon-codingsequencesoftheDNA/RNA. Genomicsisadisciplinethatapplies sequence,assemble,and yzethefunctionandstructureofgenomes.Fire-belliedsalamander(CynopsOrientalisc-value=32×109唯一可以終生進行斷蠑螈的內(nèi)含子比人類長10Annotationofgenesshowedthataxolotlintronsareonaverage10×longerthanorthologousvertebrateintronsandtheyarepredictedtocontainmorefunctionalelements,includingmiRNAsandsnoRNAs. Genesareonaverage5×largerthanhumangenes,thegeniccomponentofthesalamandergenomeisestimatedtobeincrediblylarge,approximately2.8gigabases!Thisstudyshowsthatalargesalamandergenomehasacorrespondinglylargegeniccomponent,primarilybecausegeneshaveincrediblylongintrons.Theseintronicsequencesmayharbornovelcodingandnon-codingsequencesthatregulatebiologicalprocessesthatareuniquetosalamanders.JeramiahJetal.,GenicregionsofalargeGenomics2009,10:19doi:10.1186/1471-2164-10-genomecontainlongintronsGenomics2009,10:19doi:10.1186/1471-2164-10-組secreted

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