Clonal origin of partially inactivated centromeres in a stable dicentric chromosome.

A stable dicentric human chromosome can appear to be both dicentric and monocentric, with either centromere in the primary constriction. Tetraploid cells were examined to determine if the chromosome bred true with respect to the three possible centromere configurations or if it could alternate between them. When a tetraploid cell contained two monocentric copies of the chromosome, the two copies would always have the same centromere in the primary constriction. However, some tetraploids contained one dicentric and one monocentric copy. Thus, centromere usage was fixed for the monocentric chromosomes, but it was not clear if truly dicentric chromosomes existed.