Fig. 4

Suggested mechanisms of the observed genetic disorder. a Pathogenetic activation (PA) of the maternal pronucleus is assumed as primary event with one pronucleus giving rise to the cell line with genome-wide maternal isodiploidy by endoreplication (E) and mating of the second maternal pronucleus with a sperm bearing two X chromosomes. b Retention of the second polar body (R) lead after endoreplication to the origin of the isodiploid cell line. c Failure of the paternal pronucleus to duplicate (F) could result in one biparental cell line and a second maternal haploid chromosome set that after endoreplication again could be the origin of the maternal isodiploid cell line. Black circles: biparental inheritance, pink: maternal genetic content, blue: paternal genetic content. n number of chromosome sets, c number of chromatids