The accumulation of P-elements on the tip of theXchromosome in populations ofDrosophila melanogaster

Abstract

Summary: Little information exists about the mechanisms that determine the fate of mobile elements in natural populations. In this study we catalogue the distribution of 638 P-elements across 114Xchromosomes in samples drawn from three natural populations ofDrosophila melanogaster. There is an extremely high occurrence of elements at the tip relative to the rest of the euchromatic chromosome. We demonstrate that the distribution ofde novoinsertions of the P-element on a specific laboratory chromosome is markedly different; no P-elements were recovered at the tip in the 243 insertion events recorded. In contrast, insertion data for the π²chromosome suggests an elevated rate associated with the tip site although it does not appear sufficient to explain the large differential accumulation on wild chromosomes. This raises the issue of inter chromosome (or tip) variation in relative rates, as well as the possibility that rates of elimination are lower at the tip.