Sequence complexity in the maternal RNA of the starfish Pisaster ochraceus (Brandt)☆

[摘要] ThesequencecomplexityoftheRNApresentineggsoftheseastarPisasterochraceuswasmeasuredbyRNAexcesshybridization.Single-copy125I-DNAwaspreparedbyhydroxyapatitechromatographyafterrenaturationofrandomlyshearedgenomicDNAtoC0t1000.EggRNAwasextractedbytheguanidine-HClmethod.ThetotalamountofRNAperegg,15ng,wasdeterminedbythreemethods:spectrophotometrically,byisotopicdilution,andcolorimetrically.The125I-DNAtracerwashybridizedwithalargeexcessofRNAandtheamountofDNA-RNAhybridsformedwasassayedbyhydroxyapatite.Atterminationofthereaction,whichfollowspseudo-first-orderkinetics,5.9%ofthereactablesingle-copyDNAmassispresentinDNA-RNAhybrids.Assumingasymmetrictranscription,thisrepresents11.8%ofthegenomicsingle-copycomplexity,orabout4.3×107nucleotidesofdiversesequence.Kineticanalysesindicatethatontheorderof2–3%ofthematernalRNAmassdrivesthehybridizationreaction,andeachsinglecopysequenceisrepresentedapproximately1.7×104timesperegg.

[学科分类] 生物科学（综合）