. Genetic characteristics of two families having two children with Down's syndrome were analysed in the Department of Medical Biology and Genetics - Hanoi Medical University. Results: Family 1: Couple have two sons with Down's syndrome trisomy 21. Karyotype of the father 46,XY. Karyotype of the mother 46,XY Two sons (5 years and 3 years of old) have karyotype 47,XY,+21. Two sons have single horizontal fold on both hands. Family 2: Couple have a girl and a son with Down's syndrome translocated chromosome t (13;21). Karyotype of the father: 46,XY and of the mother 45,XX,-13,+t(13;21). Karyotype of the girl (12 years): 46,XX, 13,+t(13;21). Karyotype of the son (7 years) have: 46,XY,-13, +t(13;21). Two children have not any single fold on the hands.
Down Syndrome, Child, Genes