Analysis of non-disjunction in sex chromosome tetrasomy and pentasomy

Abstract
X-linked DNA markers were used to determine the parental origin of the additional sex chromosomes in eight individuals with sex chromosome tetrasomy or pentasomy. In all cases studied, one parent contributed a single sex chromosome while the other parent contributed three or four sex chromosomes. Thus, it seems likely that most, if not all, sex chromosome tetrasomy and pentasomy is attributable to successive nondisjunctional events involving the same parent.