Alphoidless centromere of a familial unstable inverted Y chromosome.

We report on a 3-generation pedigree in which an inverted unstable Y chromosome had no phenotypical or reproductive repercussion despite a sizable proportion of secondary aneuploidies (mainly 45, X cells) in lymphocytes. This chromosome was metacentric and had a single Cd-positive primary constriction, but occasionally assumed a normal acrocentric aspect. FISH using the probe DYZ3 revealed a single strong signal; unexpectedly, the signal was outside the primary constriction and appeared to map in the middle of p, that is, at the usual centromeric localisation.