The preferential location of the human Y chromosome in somatic metaphase. I. Influence of Y polymorphism.

The location of the Y chromosome in metaphase figures was studied, with respect to its polymorphism, on 700 micrographs from blood lymphocyte cultures from 70 normal male members of seven Canadian family lines whose polymorphic Y chromosomes were inherited in a patrilinear fashion from seventeenth-century French ancestors. Three of these family lines were carriers of a long Y chromosome, two a small one, one had an average length Y and a seventh one had a satellited Y marker. The Y chromosome was peripheral in 75 to 90 per cent of the metaphase plates from each individual investigated. The long Y markers were more peripheral than the small ones while the average length Y chromosome had an intermediate position, whereas the satellited Y chromosome was located within the small group. The difference between the location of the long and the small Y chromosomes was highly significant. It is hypothesised that a heteromorphic Y might affect the nonrandom orientation of metaphasic chromosomes and favour meiotic nondisjunction and aneuploidy.