[Molecular cytogenetic study of an extra small chromosome]

An extra small chromosome was observed in a three-generation family. Eight members of this family were involved, but their phenotypes were normal. Molecular cytogenetic study was carried out, using cytogenetic methods and chromosome in situ hybridization with 3H-labelled rDNA probe. The results showed that this chromosome was from the short arm of chromosome of D/G group. The origin and genetic effects of this chromosome and fertility of the carriers were also discussed were also discussed briefly.