FAMILIAL PERICENTRIC-INVERSION INV(8)(P23Q11)

We describe two families in whom a pericentric inversion, inv(8)(p23q1 1), is segregating. No examples of unbalanced karyotypes were encounte red. The families originated from neighbouring parishes in western Fin land. In one family a mild form of mental retardation segregated. Howe ver, this phenotype did not cosegregate with the inversion karyotype. There was no evidence of a higher than average abortion rate in the in version carriers. Carrier matings produced 19 children with a balanced inversion and 14 children with a normal karyotype, concordant with a 1:1 segregation ratio. Of 13 karyotyped men at risk, 10 were inversion carriers. However, this difference was not statistically different fr om the expected 1:1 ratio. In females, the inversion carrier to normal ratio was 10:11.