Location of fourth chromosomal male-determining factors of the housefly, Musca domestica.

Two novel fourth chromosomal male-determining factors, IVM, of the housefly were mapped using a modification of the general mapping procedure for autosomal male-determining factors, AM (Inoue and Hiroyoshi 1984). On the basis of meiotic female recombination frequencies, the same gene order Barl-ye-M was demonstrated for the two IVM chromosomes. On both chromosomes, male recombination took place although at exceedingly low frequencies. From a comparison between the female and the male recombination maps, it appears that, unlike other AM factors examined so far, the two IVM factors are not located near the centromere.