Genetic control of sex determination in the germ line and soma of the housefly, Musca domestica

In Musca domestica, sex in the soma is cell autonomously determined by the male-determiner M, or by the female-determiner FD. Transplanted pole cells (precursors of the germ line) show that sex determination of germ cells is non-autonomous genotypically male pole cells form functional eggs in female hosts, and genotypically female pole cells form functional sperm in male hosts. When M/+ cells undergo oogenesis, a male-determining maternal effect predetermines offspring without M, i.e. of female genotype, to develop as fertile males. FD is epistatic to M in the female germ line, as it is in the soma, overruling the masculinizing effect of M. The results suggest that maternal F product is needed for activation of the zygotic F gene.