Regular G21-trisomy in 3 sibs from mother with trisomy 21 mosaicism.

This paper describes a family with 3 affected sibs with regular trisomy 21 Down syndrome. The condition seems to be transmitted from a phenotypically normal mother in whom G-trisomy mosaicism was identified. Giemsa banding depicted trisomy 21 mosaicism in cells from the mother. Chromosomes from the children showed a trisomy 21 in all the cells analysed.