分子生物学 名词解释.docx

分子生物学 名词解释.docx

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分子生物学名词解释

AbundanceofanmRNAistheaveragenumberofmoleculespercell.

AbundantmRNAsconsistofasmallnumberofindividualspecies,eachpresentinalargenumberofcopiespercell.

Acceptorsplicingsite—seerightsplicingjunction.

Acentricfragmentofachromosome（generatedbybreakage）lacksacentromereandislostcelldivision.

Acrocentricchromosomehasthecentromerelocatedneareroneendthantheother.

Activesiteistherestrictedpartofaproteintowhichasubstratebinds.

Alleleisoneofseveralalternativeformsofageneoccupyingagivenlocusonachromosome.

Allelicexclusiondescribestheexpressioninanyparticularlymphocyteofonlyoneallelecodingfortheexpressedimmunoglobulin.

Allostericcontrolreferstotheabilityofaninteractionatonesiteofaproteintoinfluencetheactivityofanothersite.

Alufamilyisasetofdispersed,relatedsequences,each～300bplong,inthehumangenome.TheindividualmembershaveAlucleavagesitesateachend（hencethename）.

Alu-equivalentfamilyisthesetofsequencesinamammaliangenomethatisrelatedtothehumanAlufamily.

α-AmanitinisabicyclicoctapeptidederivedfromthepoisonousmushroomAmanitaphalloides;itinhibhitstranscriptionbycertaineukaryoticRNApolymerases,especiallyRNApolymeraseII.

AmbercodonisthenucleotidetripletUAG,oneofthreecodonsthatcauseterminationofproteinsynthesis.

AmbermutaiondescribesanychangeinDNAthatcreatesanambercodonatasitepreviouslyoccupiedbyacodonrepresentinganaminoacidinaprotein.

AmbersuppressorsaremutantgenesthatcodefortRNAswhoseanticodonshavebeenalteredsothattheycanrespondtoUAGcodonsaswellasorinsteadoftotheirpreviouscodons.

Aminoacyl-tRNAistransferRNAcarryinganaminoacid;thecovalentlinkageisbetweentheNH2groupoftheaminoacidandeitherthe3’-or-2’-OHgroupoftheterminalbaseofthetRNA.

Aminoacyl-tRNAsynthetasesareenzymesresponsibleforcovalentlylinkingaminoacidstothe2’or3’-OHpositionoftRNA.

Amphipathicstructureshavetwosurfaces,onehydrophilicandonehydrophobic.Lipidsareamphipathic;andsomeproteinregionsmayformamphipathic;andsomeproteinregionsmayformamphipathichelices,withonechargedfaceandoneneutralface.

Amplificationreferstotheproductionofadditionalcopiesofachromosomalsequence,foundasintrachromosomalorextrachromoxomalDNA.

Anchoragedependencedescribestheneedofnormaleukaryoticcellsforasurfacetoattachtoinordertogrowinculture.

Aneuploidchromosomeconstitutiondifferesfromtheusaldiploidconstitutionbylossorduplicationofchromosomesorchromosomalsegments.AnnealingisthepairingofcomplementarysinglestrandsofDNAtoformadoublehelix.

Antibodyisaprotein（immunoglobulin）producedbyBlymphocytecellsthatrecognizesaparticularforeign‘antigen,’andthuswtriggerstheimmuneresponse.

AnticodingstrandofduplesDNAisusedasatemplatetodirectthesynthesisofRNAthatiscomplementarytoit.

Antigenisanymoleculewhoseentryintoanorganismprovokessynthesisofanantibody（immunoglobulin）.

Antiparallelstrandsofthedoublehelixareorganizedinoppositeorientation,sothatthe5’endofonestrandisaligenedwiththe3’endoftheotherstrand.

AntiterminationproteinsallowRNApolymerasetotranscribethroughcertainterminatorsites.

ApendonucleasesmakeincisionsinDNAonthe5’sideofeitherapurinicorapyrimidincsites.

ApoinducerisaproteinthatbindstoDNAtoswitchontranscriptionbyRNApolymerase.

Archebacteriacompriseaminorlineofprokaryotes,andmayhaveintronsinthegenome.Ascusofafunguscontainsatetradoroctadofthe（haploid）spores,representhingtheproductsofasihnglemeiosis.

attstiesarethelocionaphageandthebacterialchromosomeatwhichrecombinationintegratesthephageinto.orexcisesitfrom,thebacterialchromosome.

Attenuationdescribestheregulationofterminationoftranscriptionthatisinvolvedincontrollingtheexpressionofsomebacterialoperons.

Attenuatoristheterminatorsequenceatwhichattenuatiojoccurs.

Autogenousconhtroldescribestheactionofageneproductthateitherinhibits（negativeautogenouscontrol）oractivates（positiveautogenouscontrol）expressionofthegenecodingforit.

Autonomouscontrollingelementinmaizeisanactivetransposonwiththeabilitytotranspose（cfnonautonomouscontrollingelement）.

Autoradiographydetectsradioactivelylabeledmoleculesbytheireffectincreatinganimageonpholtographicfilm.

Autosomesareallthechromosomesexceptthesexchromosomes;adiploidcellhastwocopiesofeachautosome.

Blymphocytes（orBcells）arethecellsresponsibleforsynthesizingantibodies.

Backcrossisanother（earlier）termforatestcross.

Backmutationreversestheeffectofamutationthathandinactivatedagene;thusitrestoreswildtype.

Bacteriophagesarevirusesthatinfectbacteria;oftenabbreviatedasphages.

Balbainiringisanextremelylargepuffatabandofapolytenechromosome.

BandsofpolytenechromosomesarevisibleasdenseregionsthatcontainthemajorityofDNA;

bandsofnormalchromosomesarerelativelymuchlargerandaregeneratedintheformofregionsthatretainastainoncertainchemicaltreatments.

Basepair（bp）isapartnershipofAwithTorofCwithGinaDNAdoublehelix;otherpairscanbeformedinRNAundercertaincircumstances.

Bidirectionalreplicationisaccomplishedwhentworeplicationforksmoveawayfromthesameoriginindifferentdirections.

Bivalentisthestructurecontainingallfourchromatids（tworepresentingeachhomologue）atthestartofmeiosis.

Blastodermisastageofinsectembryogenesisinwhichalayerofnucleiorcellsaroundtheembryosurroundaninternalmassofyolk.

Blockedreadingframecannotbetranslatedintoproteinbecauseitisinterruptedbyterminationcodons.

Blunt-endligationisareactionthatjoinstwoDNAduplexmoleculesdirectlyattheirends.

bpisanabbreviationforbasepairs;distancealongDNAismeasuredinbp.

BranchmigrationdescribestheabilityofaDNAstrandpartiallypairedwithitscomplementinaduplextoextenditspairingbydisplacingtheresidentstrandwithwhichitishomologous.

Breackageandreuniondescribesthemodeofgeneticrecombination,inwhichtwoDNAduplexmoleculesarebrokenatcorrespondingpointsandthenrejoinedcrosswise（involvingformationofalengthofheteroduplexDNAaroundthesiteofjoining）.

Buoyantdesitymeasurestheabilityofasubstancetofloatinsomestandardfluid,forexample,CsCl.

Cbandingisatechniqueforgeneratingstainedregionsaroundcentromeres.

Cgenescodefortheconstantregionsofimmunoglobulinproteinchains.

CvalueisthetotalamountofDNAinahaploidgenome.

CAATboxispartofaconservedsequencelocatedupstreamofthestartpointsofeukaryotictranscriptionunits;itisrecognizedbyalargegroupoftranscriptionfactors.

Capisthestructureatthe5’endofeukaryoticmRNA,introducedaftertranscriptonbylinkingtheterminalphosphateof5’GTPtotheterminalbaseofthe mRNA.TheaddedG（andsometimessomeotherbases）aremethylated,givingastructureoftheform7MeG5’ppp5’Np…

CAP（CRP）isapositiveregulatorproteinactivatedbycyclicAMP.ItisneededforRNApolymerasetoinitiatetranscriptionofcertain（catabolitesensitive）operonsofE.coli.

Capsidistheexternalproteincoatofavirusparticle.

Cataboliterepressiondescribesthedecreasedexpressionofmanybacterialoperonsthatresultsfromadditionofglucose.ItiscausedbyadecreaseinthelevelofcyclicAMP,whichinturninactivatestheCAPregulator.

cDNAisasingle-strandedDNAcomplementarytoanRNA,synthesizedfromitbyreversetranscriptioninvitro.

cDNAcloneisaduplexDNAsequencerepresentinganRNA,carriedinacloningvector.

Cellcycleistheperiodfromonedivisiontothenext.

Cellhybridisasomaticcellcontainingchromosomesderivedfromparentalcellsofdifferentspecies（e.g.aman-mousesomaticcellhybrid）,generatingbyfusingthecellstoformaheterokaryoninwhichthenucleisubsequentlyfused.

Centriolesaresmallhollowcylindersconsistingofmicrotubulesthatbecomelocatednearthepolesduringmitosis.Theyresidewithinthecentrosomes.

Centromereisaconstrictedregionofachromosomethatincludesthesiteofattachmenttothemitoticormeioticspindle（seealsokinetochore）.

Centrosomesaretheregionsfromwhichmicrotubulesareorganizedatthepolesofamitoticcell.Inanimalcells,eachcentrosomecontainsapairofcentriolessurroundedbyadenseamorphousregiontowhichthemicrotubulesattach.SeealsoMTOC.

Molecularchaperoneisaproteinthatisneededfortheassemblyorproperfoldingofsomeotherprotein,butwhichisnotitselfacomponentofthetargetcomplex.

ChemicalcomplexityistheamountofaDNAcomponentmeasuredbychemicalassay.

ChisequenceisanoctamerthatprovidesahotspotforRecA-mediatedgeneticrecombinationinE.coli.

ChistructureisajointbetweentwoduplexmoleculesofDNArevealedbycleavinganintermediateoftwojoinedcirclestogeneratelinearendsineachcircle.ItresemblesaGreekchiinoutline,hencethename.

Chiasma（pl.chiasmata）isasiteatwhichtwohomologouschromosomesappeartohaveexchangedmaterialduringmeiosis.

Chromatidsarethecopiesofachromosomeproducedbyreplication.Thenameisusuallyusedtodescribethemintheperiodbeforetheyseparateatthesubsequentcelldivision.

ChromatinisthecomplexofDNAandproteininthenucleusoftheinterphasecell.Individualchromosomescannotbedistinguishedinit.Itwasoriginallyrecognizedbyitsreactionwithstains