Dicentric X isochromosomes in man.

Abstract

Four cases of Turner''s syndrome are presented in which an apparent X isochromosome i(Xq) possessed 2 regions of centromeric heterochromatin. These chromosomes may be isodicentric structures capable of functioning as monocentric elements as a result of the inactivation of 1 centromere. The prevalence of mosaicism is believed to be a consequence of the dicentric nature of these chromosomes, and it is considered possible that a high proportion of X isochromosomes are structurally dicentric. Banding patterns showed that the exchange site involved in the formation of the dicentric chromosome was different in at least 3 of the cases.