Cytogenetic investigation of six patients with X isochromosomes, i(Xq), and of two subjects with isodicentric X chromosomes, idic (Xq).

The detailed cytogenetic study of six Xq isochromosomes, i(Xq), and two isodicentric Xq chromosomes revealed that both their banding and their inactivation patterns differ as a result of differences in their mechanisms of origin. The arms of Xq isochromosomes may be expected to be mirror images in respect of their morphologic pattern and DNA replication sequence only in dicentric Xq isochromosomes.