This project will continue investigations of the population properties of transposable elements of Drosphila. The question of whether or not the apparent fixation of certain elements at some chromosomal sites in a D. melanogaster population is real or artefactual will be answered. Some families of D. melanogaster elements used in previous studies will be characterized by restriction mapping. This will yield information essential for the interpretation of previous work, and for other proposed experiments. A study will be made of the rates of transposition and excision of several families of D. melanogaster elements. Southern blotting and in situ hybridization of element probes will be used to detect changes in element locations in isogenic stocks that have been maintained heterozygous and sheltered from recombination for over 100 generations will also be studied. Families of transposable elements from D. americana will be cloned. These will be used to determine whether elements have accumulated an the neo-Y chromosome of this species, as expected theoretically. The proposed experiments will provide information that is fundamental to an understanding of the regulation of the abundance of transposable elements in natural populations.
