Polymorphism of M factors in populations of the housefly, Musca domestica L., in Turkey

M factors, which determine maleness in Musca domestica, were found on the s econd, third, fourth and fifth linkage groups in housefly populations of Tu rkey. As in European populations, the male-determining factor was more freq uently located on linkage group III (M-III). Some males homozygous or doubl e heterozygous for M factors were identified. Deviations from a 1:1 sex rat io in favour of males, as well as mosaics for somatic marker mutations and sexual mosaics (gynandromorphs), were also observed. The results reveal an extensive polymorphism in the sex-determining system.