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Y family study: heritable variation in the length of the human Y chromosome.

Because of considerable disagreement over the length of the human Y chromosome, it was suggested in 1960 [1] that a large amount of polymorphism may exist for this chromosome. Since then, numerous reports of individuals and populations with variant Y chromosomes have appeared which substantiate the earlier speculation. Bender and Gooch [2] first reported an exceptionally long Y chromosome in a subject with a normal phenotype; short Y chromosomes were reported by Muldal and Ockey [3]. More recently, studies of racial and ethnic subgroups have shown significant withinand between-group variation in Y chromosome length. Of the groups thus far studied, the mean length of the Japanese Y chromosome is the greatest [4], and the Australian Aborigines, the least (R. Angell, personal communication). Observations from surveys of newborns have also indicated that a large amount of polymorphism exists in human Y chromosome length (H. A. Lubs, unpublished data). Further, it has been concluded from limited family studies that the Y chromosome is inherited at a constant length [5-9]. Unfortunately, however, many of the studies either did not include precise chromosome measurements or included only a small number of families. This report describes a more complete quantification of the heritability from father to son of the length of the human Y chromosome.