Chromosomal Translocation in a Mongoloid Male Child and His Normal Mother.

The presence of 47 chromosomes in mongoloids, due to the trisomy of a small acrocentric chromosome in the 21-22 group (Denver system) was demonstrated by Lejeune et al. 1 1 in 1959, and since that time has been confirmed by numerous authors (Beçak 2 ) . The production of this trisomy is explained by a defect in the process by which the homologous chromosomes or sister chromatids should dislocate from the opposing poles during the gametogenesis. Non disjunction which results in the trisomy of 21 chromosome generally occurs in individuals with normal karyotypes and is influenced by etiological factors associated with maternal age.