[Results of estimation of mutation rates for translocation trisomy 21].

Among 1332 cases of trisomy 21 born within 1979-1999 in St. Petersburg, 76(5.7%) were carriers of a translocation between chromosome 21 and other acrocentrics.

[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.

[Polymorphism of C-heterochromatin chromosome regions in the etiology of human aneuploidy].

Cytogenetic study of the C-heterochromatic polymorphisms in 202 individuals from the Down's syndrome families and in 31 control individuals was undertaken. In 58 families the source of an additional chromosome was taken into account. It was shown that in the donors of extra chromosome, due to nondisjunction in the Ist meiotic division, the frequency of heteromorphism was higher (0.

[Multiple chromosome aberrations in 3 generations of a family and Down's syndrome resulting from partial trisomy of chromosome 21 (q21--q22)].

Two balanced translocations (1; 16) (q22; q11) and t(21; 22) (q21; p11), partial inversion of chromosome 9 and variant 16gh + were detected in the family of the child with Down's syndrome. The proband clinical picture was due to trisomy of the distal region of the long arm of chromosome 21 (q21----q22). Proband's karyotype was 46, XY, --22, +der(22), t(21; 22)mat, inv(9).

[Rare structural rearrangement of the Y chromosome (Yq-,S) in the family of a boy with a sex differentiation disorder].

In an 8-year old boy with bilateral cryptorchism the heterochromatin region deletion of Y-chromosome and the satellites in its long arm were found (karyotype 46, XYq-S). The same Y-chromosome was found in proband's father. Moreover, the proband had large brilliant satellites in the chromosome 22 and a very large segment of centromeric heterochromatin in the chromosome 1; both were inherited from his mother.