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生物信息学主要英文术语及释义CodingregionofDNA.SeeCDS.ExpressedSequenceTag(EST)（表达序列标签）Randomlyselected,partialcDNAsequence;representsit'scorrespondingmRNA.dbESTisalargedatabaseofESTsatGenBank,NCBI.FASTA（一种主要数据库搜索程序）Thefirstwidelyusedalgorithmfordatabasesimilaritysearching.Theprogramlooksforoptimallocalalignmentsbyscanningthesequenceforsmallmatchescalledwords.Initially,thescoresofsegmentsinwhichtherearemultiplewordhitsarecalculated(init1).Laterthescoresofseveralsegmentsmaybesummedtogenerateaninitnscore.Anoptimizedalignmentthatincludesgapsisshownintheoutputasopt.Thesensitivityandspeedofthesearchareinverselyrelatedandcontrolledbythek-tupvariablewhichspecifiesthesizeofaword.(PearsonandLipman)Extremevaluedistribution（极值分布）Somemeasurementsarefoundtofollowadistributionthathasalongtailwhichdecaysathighvaluesmuchmoreslowlythanthatfoundinanormaldistribution.Thisslow-fallingtypeiscalledtheextremevaluedistribution.Thealignmentscoresbetweenunrelatedorrandomsequencesareanexample.Thesescorescanreachveryhighvalues,particularlywhenalargenumberofcomparisonsaremade,asinadatabasesimilaritysearch.Theprobabilityofaparticularscoremaybeaccuratelypredictedbytheextremevaluedistribution,whichfollowsadoublenegativeexponentialfunctionafterGumbel.Falsenegative（假阴性）Anegativedatapointcollectedinadatasetthatwasincorrectlyreportedduetoafailureofthetestinavoidingnegativeresults.Falsepositive（假阳性）Apositivedatapointcollectedinadatasetthatwasincorrectlyreportedduetoafailureofthetest.Ifthetesthadcorrectlymeasuredthedatapoint,thedatawouldhavebeenrecordedasnegative.Feed-forwardneuralnetwork（反向传输神经网络）Organizesnodesintosequencelayersinwhichthenodesineachlayerarefullyconnectedwiththenodesinthenextlayer,exceptforthefinaloutputlayer.Inputisfedfromtheinputlayerthroughthelayersinsequenceina“feed-forward”direction,resultinginoutputatthefinallayer.SeealsoNeuralnetwork.Filtering(windowsize)Duringpair-wisesequencealignmentusingthedotmatrixmethod,randommatchescanbefilteredoutbyusingaslidingwindowtocomparethetwosequences.Ratherthancomparingasinglesequencepositionatatime,awindowofadjacentpositionsinthetwosequencesiscomparedandadot,indicatingamatch,isgeneratedonlyifacertainminimalnumberofmatchesoccur.Filtering（过滤）AlsoknownasMasking.Theprocessofhidingregionsof(nucleicacidoraminoacid)sequencehavingcharacteristicsthatfrequentlyleadtospurioushighscores.SeeSEGandDUST.Finishedsequence（完成序列）Completesequenceofacloneorgenome,withanaccuracyofatleast99.99%andnogaps.FourieranalysisStudiestheapproximationsanddecompositionoffunctionsusingtrigonometricpolynomials.Format(file)（格式）Differentprogramsrequirethatinformationbespecifiedtotheminaformalmanner,usingparticularkeywordsandordering.Thisspecificationisafileformat.Forward-backwardalgorithmUsedtotrainahiddenMarkovmodelbyaligningthemodelwithtrainingsequences.Thealgorithmthenrefinesthemodeltoreducetheerrorwhenfittedtothegivendatausingagradientdescentapproach.FTP(FileTransferProtocol)（文件传输协议）AllowsapersontotransferfilesfromonecomputertoanotheracrossanetworkusinganFTP-capableclientprogram.TheFTPclientprogramcanonlycommunicatewithmachinesthatrunanFTPserver.Theserver,inturn,willmakeaspecificportionofitstilesystemavailableforFTPaccess,providingthattheclientisabletosupplyarecognizedusernameandpasswordtotheserver.Fullshotgunclone（鸟枪法克隆）Alarge-insertcloneforwhichfullshotgunsequencehasbeenproduced.Functionalgenomics（功能基因组学）Assessmentofthefunctionofgenesidentifiedbybetween-genomecomparisons.Thefunctionofanewlyidentifiedgeneistestedbyintroducingmutationsintothegeneandthenexaminingtheresultantmutantorganismforanalteredphenotype.gap（空位/间隙/缺口）Aspaceintroducedintoanalignmenttocompensateforinsertionsanddeletionsinonesequencerelativetoanother.Topreventtheaccumulationoftoomanygapsinanalignment,introductionofagapcausesthedeductionofafixedamount(thegapscore)fromthealignmentscore.Extensionofthegaptoencompassadditionalnucleotidesoraminoacidisalsopenalizedinthescoringofanalignment.Gappenalty（空位罚分）Anumericscoreusedinsequencealignmentprogramstopenalizethepresenceofgapswithinanalignment.Thevalueofagappenaltyaffectshowoftengapsappearinalignmentsproducedbythealgorithm.Mostalignmentprogramssuggestgappenaltiesthatareappropriateforparticularscoringmatrices.Geneticalgorithm（遗传算法）Akindofsearchalgorithmthatwasinspiredbytheprinciplesofevolution.Apopulationofinitialsolutionsisencodedandthealgorithmsearchesthroughthesebyapplyingapre-definedfitnessmeasurementtoeachsolution,selectingthosewiththehighestfitnessforreproduction.Newsolutionscanbegeneratedduringthisphasebycrossoverandmutationoperations,definedintheencodedsolutions.Geneticmap（遗传图谱）Agenomemapinwhichpolymorphiclociarepositionedrelativetooneanotheronthebasisofthefrequencywithwhichtheyrecombineduringmeiosis.Theunitofdistanceiscentimorgans(cM),denotinga1%chanceofrecombination.Genome（基因组）Thegeneticmaterialofanorganism,containedinonehaploidsetofchromosomes.GibbssamplingmethodAnalgorithmforfindingconservedpatternswithinasetofrelatedsequences.Aguessedalignmentofallbutonesequenceismadeandusedtogenerateascoringmatrixthatrepresentsth