sex chromosome mosaic, an individual or organism whose cells contain variant chromosomal numbers involving the X or Y chromosomes. Such variations occur in most of the syndromes associated with sex chromosome aberrations, primarily Turner’s syndrome, and may be caused by nondisjunction of the chromosomes during the second meiotic division of gametogenesis or by some error in chromosome distribution during cell division of the fertilized ovum. Sex chromosome mosaics often have sexual abnormalities, but because of the sex hormones the overall phenotype is uniform and not mosaic in external characteristics, as in certain animals and insects. Also called sex mosaic. See also intersexuality.
