Down's syndrome and deletion of short arms of a G chromosome.

A woman in a family in which a G group chromosome (No. 21) with deleted short arms (21p-) is present has passed this chromosome to an intellectually deficient son, a normal son, and a daughter with Down's syndrome. Another daughter is chromosomally and phenotypically normal. As in other reports that focus on a concurrence of Gp- chromosomes and Down's anomaly, the possibility is considered that this chromosomal variant may predispose to developmental abnormalities or to non-disjunction, or both.