简介：Microsatellitesorsimplesequencerepeats(SSRs)havebeenfoundinmostorganismsduringthelastdecade.Sincelarge-scalesequencesarebeinggenerated,especiallythosethatcanbeusedtosearchformicrosatellites,thedevelopmentofthesemarkersisgettingmoreconvenient.KeepingSSRsinviewingtheimportanceoftheapplication,availableCDS(codingsequences)orESTs(expressedsequencetags)ofsomeeukaryoticspecieswereusedtostudythefrequencyanddensityofvarioustypesofmicrosatellites.OnthebasisofsurveyingCDSorESTsequencesamountingto66.6Mbinsilkworm,37.2Mbinfly,20.8Mbinmosquito,60.0Mbinmouse,34.9Mbinzebrafishand33.5MbinCaenorhabditiselegans,thefrequencyofSSRswas1/1.00Kbinsilkworm,1/0.77Kbinfly,1/1.03Kbinmosquito,1/1.21Kbinmousey1/1.25Kbinzebrafishand1/1.38KbinC.Elegans.TheoverallaverageSSRfrequencyofthesespeciesis1/1.07Kb.Hexanucleotiderepeats(64.5％-76.6％)arethemostabundantclassofSSRintheinvestigatedspecies,followedbytrimeric,dimeric,tetrameric,monomericandpentamericrepeats.Furthermore,theA-richrepeatsarepredominantineachtypeofSSRs,whereasG-richrepeatsarerareinthecodingregions.