Size variation in kinetochores of human chromosomes.

Aneuploidy, the loss or gain of chromosomes from cells, is likely in many cases to involve the kinetochore, the site of attachment of spindle microtubules. We analyzed human fibroblast cells with antikinetochore-antibody indirect immunofluorescence, and noted an apparent heterogeneity in the sizes of kinetochores among different chromosomes. The Y chromosome in particular always showed minute kinetochores, an observation which was quantified and substantiated using computer-assisted image analysis. This finding, combined with literature reports about in vivo and in vitro involvement of the Y chromosome in aneuploidy, was used to frame a novel hypothesis about the generation of chromosome imbalance.