CHROMOSOME MOSAICISM IN A ZEBRA (EQUUS-BURCHELLI) ABORTUS PROVIDES EVIDENCE FOR A DIFFERENT INVIVO INVITRO SURVIVAL OF BALANCED AND UNBALANCED KARYOTYPES

Summary. A fibroblast culture from the skin of a zebra abortus recovered from a pedigree known, in part, to be segregating for a chromosome centric fission was karyotypically mosaic. Some cells were balanced for the fission and the others unbalanced, being deficient for the shorter fission product. Initially, the latter were in the majority but after continued culture (101 days) they were outgrown by the former. This finding either suggests a differential in-vivo/in-vitro fitness of the two cell types or a change in proportions resulting from some other mechanism.