[Karyological characteristics of Down's syndrome: clinical and theoretical aspects].

These data have been collected from St. Petersburg Down Syndrome Register that comprises information on 1778 liveborn children with the Down syndrome, including three twin sets, ascertained within 1970-1996. Karyotypes were obtained in 1223 cases, of which 1119 (90.

[Mutational level of translocated variants of Down's syndrome in Leningrad (1982-1991)].

Karyological study of 644 newborns with Down's syndrome (DS) revealed 37 translocation cases (5.7%). Translocations were inherited in 8 cases, in 17 cases they were sporadic, and in 12 cases parents were not examined.