NOR activity and satellite association patterns in a family carrying a doubly satellited marker

Activity and association patterns of nucleolar organizer regions (NORs) were studied in cultured blood lymphocytes from six members of a family, three of whom carried a doubly satellited marker. The marker consisted of a centromere with two sets of satellites and stalks which showed consistent NOR activity. The children with the marker had significantly higher frequencies of NOR activity and satellite association than their non-carrier siblings. The acrocentrics of the children with the marker did not appear to have decreased association tendency.