9520572 BRYANT The normal male karyotype of the housefly, Musca domestica, consists of five pairs of autosomes and a pair of dimorphic sex chromosomes. Some males however have two X chromosomes and a portion of the Y chromosome containing the male determining factor attached to one of the third autosomes. This new male karyotype which was rare or absent fifty years ago is now found around the world and has replaced the normal male karyotype in many populations. Surveys suggest that the third chromosome containing the translocated male determining factor decreases with latitude and overall frequencies continue to increase with time. Since genetic recombination is normally absent in male houseflies, the third autosome containing the translocated male determining factor is prevented from exchanging genetic material via crossing over. Theory predicts that this should result in the accumulation of mutations on this chromosome causing it to diverge from normal third chromosomes. This study is concerned with determining how much the new male determining chromosome in the housefly has changed since the acquisition of the male determining factor. This study will survey the frequency of the new male determining chromosome from several different populations from around the U.S. Strains containing the translocated male determining factor on the third autosome will be studied and compared in terms of the accumulation of deleterious mutations, gene inactivation and dosage compensation. The accumulation of sexually antagonistic alleles associated with the new male determining chromosome will also be investigated.
