AbstractDegenerate primers designed and synthesized based on two conserved regions of themarinertransposase open reading frame were used to amplify a 454 bp DNA fragment fromM. occidentalis.Two inverse primers were then synthesized and used to amplify flanking genomic DNA fragments fromM. occidentalisby a ligation‐mediated inverse PCR. The completemarinerelement(Moc 1)was 1284 bp long, including the imperfect 28 bp inverted terminal repeat sequences, and shared 59% similarity to an active 1286 bp longD. mauritiana marinerelement(Mos 1).Insertions, deletions and substitutions were observed in theMoc 1sequence at several positions. No intact open reading frame was detected and theMoc 1element is considered inactive. Stringent Southern blot hybridizations revealed at least twelve copies ofmarinersequences similar toMoc 1in the colonies teste