A P element-homologous sequence in the house fly, Musca domestica

Sequences homologous to the P transposable element have been identified in Musca domestica, Sequence analysis of a genomic clone (Md-P1) indicates tha t, although the house fly P element has lost its coding capacity, the basic general structure of drosophilid P elements is present. The house fly P el ement sequence shares a number of structural features with that from the bl ow fly, Lucilia cuprina, including a large intron separating exons 1 and 2, two additional introns interrupting exon 2 and the apparent absence of inv erted repeat termini. Within a relatively well-conserved central region, th e house fly sequence shows 59% similarity to the D. melanogaster P element, but distal regions are more diverged. Southern blot analysis of several st rains indicated the presence of at least four P element copies.