Y chromosomen.

1911 Biol. Bull. Jan. 119 We have associated the X and Y chromosomes of the male with sex-determination, but possibly they have some other meaning.

1933 R. H. Wolcott Animal Biol. lxxiii. 537 In fowls and in moths females have either one x-chromosome or both an x-chromosome and a y-chromosome, while the males have the two x-chromosomes.

1965 R. P. Morehead Human Pathol. vi. 170/1 Proved cases of mutation involving the Y chromosome are extremely rare... As Y chromosomes occur only in males, the characteristic pedigree of such mutations should contain only affected males, never affected females, and all affected males should transmit the defect to all their sons.

1974 P. Cave Dirtiest Picture Postcard x. 57 You've buttonholed me to give me long and boring lectures upon Germaine Greer, the faulty Y chromosome and the drudgeries of housework and child~bearing.

1982 Nature 2 Dec. 404/2 When a Y chromosome is present the foetal gonad, which has the potential to become either ovary or testis, differentiates into a testis and, when absent, into an ovary... Recent genetic analysis shows that this first step is not as simple as first thought and appears to be controlled by an interaction between autosomal genes and a gene(s) on the Y chromosome, for normal male differentiation.

1983 J. R. S. Fincham Genetics ii. 72 In grasshoppers and other insects of the order Orthoptera..there is usually no Y-chromosome. The females are XX and the males just X.