Transposition of minisatellite-like DNA in Chironomus midges.

Cla elements are a family of tandem repetitive DNA sequences present in the genome of several Chironomus species. Interspersed clusters of Cla elements are widely distributed all over the chromosomes in C. thummi thummi, while they seem to be limited to the centromeric regions in the closely related subspecies C. t. piger. Here we present molecular evidence that this differential distribution is due to a transposition of Cla elements during evolution of the C. t. thummi genome. We have cloned a "filled" integration site (containing a Cla element cluster) from C. t. thummi and the corresponding "empty"genomic site from C. t. piger and other related species. The comparison shows that tandem repetitive elements may be mobilized together with flanking DNA.