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AbstractSyntaxNotation(ASN.l)（NCBI发展的许多程序，如显示蛋白质三维结构的Cn3D等所使用的内部格式）Alanguagethatisusedtodescribestructureddatatypesformally,Withinbioinformatits,ithasbeenusedbytheNationalCenterforBiotechnologyInformationtoencodesequences,maps,taxonomicinformation,molecularstructures,andbiographicalinformationinsuchawaythatitcanbeeasilyaccessedandexchangedbycomputersoftware.Accessionnumber（记录号）AuniqueidentifierthatisassignedtoasingledatabaseentryforaDNAorproteinsequence.Affinegappenalty（一种设置空位罚分策略）Agappenaltyscorethatisalinearfunctionofgaplength,consistingofagapopeningpenaltyandagapextensionpenaltymultipliedbythelengthofthegap.Usingthispenaltyschemegreatlyenhancestheperformanceofdynamicprogrammingmethodsforsequencealignment.SeealsoGappenalty.Algorithm（算法）Asystematicprocedureforsolvingaprobleminafinitenumberofsteps,typicallyinvolvingarepetitionofoperations.Oncespecified,analgorithmcanbewritteninacomputerlanguageandrunasaprogram.Alignment（联配/比对/联配）Referstotheprocedureofcomparingtwoormoresequencesbylookingforaseriesofindividualcharactersorcharacterpatternsthatareinthesameorderinthesequences.Ofthetwotypesofalignment,localandglobal,alocalalignmentisgenerallythemostuseful.SeealsoLocalandGlobalalignments.Alignmentscore（联配/比对/联配值）Analgorithmicallycomputedscorebasedonthenumberofmatches,substitutions,insertions,anddeletions(gaps)withinanalignment.ScoresformatchesandsubstitutionsArederivedfromascoringmatrixsuchastheBLOSUMandPAMmatricesforproteins,andaftinegappenaltiessuitableforthematrixarechosen.Alignmentscoresareinlogoddsunits,oftenbitunits(logtothebase2).Higherscoresdenotebetteralignments.SeealsoSimilarityscore,Distanceinsequenceanalysis.Alphabet（字母表）Thetotalnumberofsymbolsinasequence-4forDNAsequencesand20forproteinsequences.Annotation（注释）Thepredictionofgenesinagenome,includingthelocationofprotein-encodinggenes,thesequenceoftheencodedproteins,anysignificantmatchestootherProteinsofknownfunction,andthelocationofRNA-encodinggenes.Predictionsarebasedongenemodels;e.g.,hiddenMarkovmodelsofintronsandexonsinproteinsencodinggenes,andmodelsofsecondarystructureinRNA.AnonymousFTP（匿名FTP）WhenaFTPserviceallowsanyonetologin,itissaidtoprovideanonymousFTPser-vice.AusercanlogintoananonymousFTPserverbytypinganonymousastheusernameandhisE-mailaddressasapassword.MostWebbrowsersnownegotiateanonymousFTPlogonwithoutaskingtheuserforausernameandpassword.SeealsoFTP.ASCIITheAmericanStandardCodeforInformationInterchange(ASCII)encodesunaccentedlettersa-z,A-Z,thenumbersO-9,mostpunctuationmarks,space,andasetofcontrolcharacterssuchascarriagereturnandtab.ASCIIspecifies128charactersthataremappedtothevaluesO-127.ASCIItilesarecommonlycalledplaintext,meaningthattheyonlyencodetextwithoutextramarkup.BACclone（细菌人工染色体克隆）BacterialartificialchromosomevectorcarryingagenomicDNAinsert,typically100–200kb.Mostofthelarge-insertclonessequencedintheprojectwereBACclones.Back-propagation（反向传输）Whentrainingfeed-forwardneuralnetworks,aback-propagationalgorithmcanbeusedtomodifythenetworkweights.Aftereachtraininginputpatternisfedthroughthenetwork,thenetwork’soutputiscomparedwiththedesiredoutputandtheamountoferroriscalculated.Thiserrorisback-propagatedthroughthenetworkbyusinganerrorfunctiontocorrectthenetworkweights.SeealsoFeed-forwardneuralnetwork.Baum-Welchalgorithm（Baum-Welch算法）AnexpectationmaximizationalgorithmthatisusedtotrainhiddenMarkovmodels.Baye’srule（贝叶斯法则）Formsthebasisofconditionalprobabilitybycalculatingthelikelihoodofaneventoccurringbasedonthehistoryoftheeventandrelevantbackgroundinformation.IntermsoftwoparametersAandB,thetheoremisstatedinanequation:Thecondition-alprobabilityofA,givenB,P(AIB),isequaltotheprobabilityofA,P(A),timestheconditionalprobabilityofB,givenA,P(BIA),dividedbytheprobabilityofB,P(B).P(A)isthehistoricalorpriordistributionvalueofA,P(BIA)isanewpredictionforBforaparticularvalueofA,andP(B)isthesumofthenewlypredictedvaluesforB.P(AIB)isaposteriorprobability,representinganewpredictionforAgiventhepriorknowledgeofAandthenewlydiscoveredrelationshipsbetweenAandB.Bayesiananalysis（贝叶斯分析）Astatisticalprocedureusedtoestimateparametersofanunderlyingdistributionbasedonanobserveddistribution.SeealsoBaye’srule.Biochips（生物芯片）Miniaturizedarraysoflargenumbersofmolecularsubstrates,oftenoligonucleotides,inadefinedpattern.TheyarealsocalledDNAmicroarraysandmicrochips.Bioinformatics（生物信息学）Themergerofbiotechnologyandinformationtechnologywiththegoalofrevealingnewinsightsandprinciplesinbiology./Thedisciplineofobtaininginformationaboutgenomicorproteinsequencedata.Thismayinvolvesimilaritysearchesofdatabases,comparingyourunidentifiedsequencetothesequencesinadatabase,ormakingpredictionsaboutthesequencebasedoncurrentknowledgeofsimilarsequences.DatabasesarefrequentlymadepublicallyavailablethroughtheInternet,orlocallyatyourinstitution.Bitscore（二进制值/Bit值）ThevalueS'isderivedfromtherawalignmentscoreSinwhichthestatisticalpropertiesofthescoringsystemusedhavebeentakenintoaccount.Becausebitscoreshavebeennormalizedwithrespecttothescoringsystem,theycanbeusedtocomparealignmentscoresfromdifferentsearches.Bitu