Analysis of a familial 15p + polymorphism: exclusion of Y/15 translocation

A large 15p + chromosome with a whole heterochromatic short arm has been studied by means of different banding techniques in six of nine individuals of a family; a possible Y/15 translocation has been excluded. Furthermore a heteromorphic pair 9 has been observed in seven family members, representing a "possible" small partial inversion 9q12;p11 or a centromeric variation. The transmission of these variant chromosomes as well as of some h + acrocentric chromosomes over three generations could be demonstrated. By means of AgI-staining large intercellular variation of Ag-NORs of the variant acrocentrics has been observed in the family members studied. The unusual accumulation of these variant chromosomes had no phenotypic effects.