Direct determination of retrotransposon transposition rates inDrosophila melanogaster

Abstract

SummaryRates of transposition and excision of theDrosophila melanogasterretrotransposon elementsmdg3, 297, Doc, rooandcopiawere estimated directly, byin situhybridization analysis of their cytological insertion sites in 31 replicates of a highly inbred line that had accumulated spontaneous mutations for approximately 160generations. Estimated transposition rates ofDoc, rooandcopiawere, respectively, 4·2 × 10−5, 3·1 × 10−3and 1·3 − 10−3; no transpositions of297normdg3were observed. Rates of transposition ofcopiavaried significantly among sublines. Excisions were only observed forrooelements, at a rate of 9·0 × 10−6per element per generation. Copy number averaged over these element families increased 5·9 %; therefore, in these lines the magnitude of the forces opposing transposable element multiplication were weaker than transposition rates.