Inheritance of cytogenetic and new genetic markers in Megasella scalaris, a fly with an unusual sex determining mechanism

Megaselia scalaris has a karyotype of two metacentric chromosome pairs, indistinguishable from one another, and an acrocentric chromosome pair. All three pairs can carry the male determining factor (Mainx, 1966; Tokunaga, 1955b). Seven cytogenetic markers, translocations T1-T7, and three new genetic markers, ge, By and sh, were isolated and characterized during this study. The translocations involved two or all three chromosomes of a haploid chromosome set. All translocations recovered were male specific, transmitted from father to all sons. This allowed us to locate the male determining factor, M, on one of the two metacentric chromosomes in our strain 'Wien'. By crossing the new gene mutants with the cytogenetic markers, the autosomal mutants ge and By could be located to the acrocentric chromosome, and the partially sex-linked mutant sh to a metacentric. The results are intended to serve as a framework to fit in molecular markers.