Agronomy and Horticulture, Department of


Document Type


Date of this Version



Genetics 6 (1921), pp 417-432.


Copyright 1921 the authors.


One of the early developments in the study of linkage in Drosophila was the discovery that the phenomenon of crossing over is confined to the female sex (Morgan 1912). The fact that no crossing over occurs in the male Drosophila holds true not only for sex-linked genes but for factors in the autosomes as well and is so well established that it affords a most convenient method of determining to which of the different linkage groups a new factor belongs.

The same phenomenon, but with the sexes reversed, obtains in the silkworm moth. Tanaka (1914, 1915) has found from back-cross tests of both sexes in this organism, that crossing over occurs in the male but not in the female. Similarly Goodale (1917) has observed crossing over in the sex chromosome of the male fowl but none in the female and more recently Cole and Kelley (1919) have reported that crossing over occurs in the male pigeon but not in the female. In the latter case back-cross tests were made of both sexes though the number of progeny from back-cross F1 females to double-recessive males is not large. In the experiments with fowls Goodale made back-cross tests with the F1 males but not with the F1 females. No crossing over in the females, however, was noted in any of his original crosses.