[Spontaneous polyploidy in laboratory mice. Embryological and cytogenetic analysis]

The developmental patterns of mice with spontaneous genomic aberrations at the pre- and post-implantation embryonic stages have been studied. The frequency of spontaneous triploidy varies in different strains from 1.7 to 5.8%. Digeny is the principal cytogenetical mechanism for triploidy. The triploid embryos of all the strains under study are characterized by the total delay of development already at the blastocyst stage. The most of triploids die at the stages of neurula and beginning of active organogenesis. A few triploids are resorbed during placentation. In the CBA mice, the triploidization results in the characteristic syndrome: disproportionally reduced amniotic vesicle, hypertrophied allantoic rudiment, reduction of neural plate, absence of head folds, notochord and mesenchyme. The spontaneous tetraploidy in mice occurs very rarely and is accompanied by severe developmental defects already at the preimplantation stages.