Heredity 1(1): 65-83 (1947)
COLOUR INHERITANCE AND SEX DETERMINATION IN LEBISTES
By Ø. WINGE and E. DITLEVSEN
Carisberg Laboratory, Copenhagen, Valby

pp. 81-82

The present results agree fully with the assumption of multiple sex genes in the autosomes and particularly strong sex-determining genes in X and Y. On crossing an XY female, possessing a particularly strong female autosomal set of genes, with an XX male which has a particularly strong male autosomal set of genes we get an F1 with marked heterozygosity. The strongly female autosomes from the mother meet with a set of strongly male autosomes from the father, and these two sets balance each other so that the sex determination now depending on the X and Y chromosomes becomes normal both in the sons and in the daughters.

It was to be expected that the sex determination would be normal also in F2, at any rate as long as the number of individuals was not very great; it is not surprising that a single XX male may segregate out when an F1 male is mated to a female with strongly male autosomes.

On the other hand, if we were to explain the abnormal sex types by assuming variation in the strength of a single gene we would undoubtedly have to expect a segregation of XY females and XX males in F2. If, as suggested by Goldschmidt in a private communication to the senior author in 1935 concerning the XX males, as in the case of Lymantria we were to introduce a plasmatic factor M and assume this to vary from one race to another and that a particularly weak M was present in the XY female, we would have to expect that in the inbred F2 one-half of the XY individuals would be females and on crossing an F1 male with a female of the strongly male race we would have to expect one-half of the XX individuals to be males. But it does not turn out this way.

So we will have to maintain that the view of the sex determination advanced by us (Winge, 1934) is correct. The Y chromosome contains a strong male-determining gene, while the X chromosomes contain a female-determining gene, and sex-determining genes of varying potency are furthermore distributed over the autosomes in such a way that the sex determination normally depends on X and Y. XX males appear when, through recombination including crossing-over, particularly strong male-determining genes have accumulated in the autosomes ; and XY females appear when sufficiently strong female-determining genes have accumulated in an XY individual. It will be appropriate here to recall that a quite similar distribution of the sex-determining elements has been found in Melandrium (Winge, 1931). In this plant, furthermore, the study of polyploid forms has shown that the Y chromosomes contain strong male-determining genes (Warmke and Blakeslee, 1939; Westergaard, 1940). According to Westergaard, in Melandrium the sex is determined by "a very strong male-determining element in Y and a female-determining element distributed in the X chromosome and in the autosomes. Moreover, at any rate, some of the autosomes must contain male-determining genes." As will be noticed, this corresponds rather closely to the distribution of the sex genes in Lebistes.