The Y* PAR chromosome has resulted from an end to end fusion of an X and a Y PAR. Furthermore, it was shown that in conjuction with this PAR-PAR fusion, there has been a deletion of both copies of the distally located pseudoautosomal gene Steroid sulfatase (Sts). The arrangement of the two PAR regions permits reciprocal translocation of X and Y chromatin at every meiotic event in the male resulting in half of the sperm produced bearing one of two abnormal sex chromosome. (J:60, J:48823)