THE GENOMES OF MOST ANIMALS HAVE MULTIPLE MEMBERS OF THE TC1 FAMILY OF TRANSPOSABLE ELEMENTS

A PCR assay was employed to detect sequences homologous to the transpo sase gene of the Tc1 family of transposable elements in a wide variety of animals. Amplification products of the appropriate size were obtai ned from most insects (92 of 108 examined; 85%), most other invertebra tes (33 of 43; 77%), and many vertebrates (18 of 36; 50%). Sequencing a sample of cloned PCR products from eight insects, one hydra, and two frogs revealed that each had multiple distinct members of the family in their genomes. In the most extreme case, the horn fly Haematobia ir ritans yielded evidence of seventeen distinct types of Tc1 family elem ents. Most of the sequences obtained indicate that the elements are wi thin the range of variation already known from fungi, nematodes, flies , fish and frogs. Some, however, had novel length variants or divergen t sequences, indicating that they represent new subfamilies of these t ransposons. These results indicate that this family of transposons is extremely common in animal genomes, with multiple representatives in m ost genomes.