Male crossing-over and location of the male determining factor on the third chromosome in a IIIm-type strain of the housefly.

Abstract

A dominant wing-shape mutation, Bx2 (Beadex2), occurring on the IIIMchromosome was found in a wild-type housefly strain named Nagai. By backcrossing hybrid males between the Bx2 male and the third chromosomal mutant bwb ge females to the homozygous recessive mutant females, a new type of sex-limited strain designated as "bwb ge/Bx2 M(Nagai)" was established. The strain usually kept producing only male progeny with Bx2 phenotype and the female progeny with bwb ye phenotype, but the recombinant type offspring also segregated although the frequency was very low. Further analyses of these recombinants indicated that some of them were the resultants of crossing-over in the male parents, but the others were not. By using the male crossing-over data, the location of the male determining factor on the third chromosome was estimated to be the right side of ge locus.

A male-determining factor on autosome 1 and occurrence of male-recombination in the housefly, Musca domestica L..

“…On the other hand, the occurrence of male-recombination, although the rate is extremely low as compared with that of the female, has frequently been observed in anomalous XX-type males carrying autosomal male-determining factors (AM) such as JJM, 111M and VM Fukumori and Hiroyoshi 1977;Hiroyoshi et al 1982). Hence, we set up mating experiments to determine whether XX-males heterozygous for the IM-chromosome extracted from the SDF strain and a acv by marker chromosome produce recombinants or not.…”

Mapping of autosomal male-determining factors of the housefly, Musca domestica L., by means of sex-reversal.

“…This discrepancy seems to be due to the dearth of meiotic recombination in the vicinity of M locus in the sex-reversed females. For this reason, the AM loci so far estimated on the basis of male-recombination frequency (Hiroyoshi and Fukumori 1976;Inoue and Hiroyoshi 1982;Hiroyoshi, Fukumori and Inoue 1982) should not be directly assigned to the female recombination map at the present time. The male and the female recombination maps in Drosophzla melanogaster differ greatly in the heterochromatic regions, especially near the centromeres, of the chromosomes (For a review, see Becker 1976).…”

“…One approach which has been used to map AM factors is based on the rare occurrence of recombination in the XX males heterozygous for the AM chromosome and an appropriate marker chromosome (Hiroyoshi and Fukumori 1976;Inoue and Hiroyoshi 1982;Hiroyoshi, Fukumori and Inoue 1982). Another method has made use of the AM-carrying but sex-reversed females as a result of the concomitant presence of a female determining factor (F) (Rubini and Franco 1972).…”

Mapping of autosomal male-determining factors of the housefly, Musca domestica L., by using a female-determining factor.

“…In earlier studies, the locations of some AM factors have been estimated on the basis of exceptional male-recombination Hiroyoshi, Fukumori and Inoue 1982), and only one IIIM factor in a female heterogametic strain has been mapped on the basis of female recombination with the help of karyological analysis (Rubini and Franco 1972). These methods, however, required much labour for locating the AM factors.…”