Kinetochore development in two dicentric chromosomes in man. A light and electron microscopic study

Two dicentric human chromosomes were investigated with light and electron microscopic techniques. One chromosome, with a translocation tdic(5;13)(p12;p12), behaved as a dicentric in about half the cells: it had two primary constrictions; C- and Cd-banding showed two centromeres; and the CREST antikinetochore antibody reacted with the two centromeres with equal affinity. Electron microscopic analysis of sectioned metaphases showed that the dicentric could develop kinetochores at both centromeres simultaneously. The other dicentric chromosome, tdic(21;21)(q22;q22), occasionally showed two primary constrictions, but both C- and Cd-banding distinguished between an active and an inactive centromere, and the CREST antibody reacted only weakly with the inactive centromere. Electron microscopy showed kinetochore development at only one centromere.