The problem of partial endoreduplication.

Partial endoreduplication (PE) as defined by Lejeune et al. (1966) has only been found in a few instances. Similar configurations, also called PEs, seem to originate from a different process. A series of 12 PEs is presented in this paper, discovered in metaphases from healthy individuals, and in patients with or without chromosome-breakage syndrome and after treatment with chromosome-breaking agents. Interpretations of the microscopic appearance of each configuration led to the conclusion that there are three different modes of origin for such rare events, one being true partial endoreduplication, the second a partial pseudoendoreduplication, and the third a homologous triradial chromatid translocation.