New insights into triploidy and tetraploidy, from an analysis of model systems for these conditions

While triploids and tetraploids together probably account for approximately 20% of all spontaneous abortions with a numerical chromosomal defect, and consequently give rise to a significant proportion of human pregnancy wastage, relatively little is known about their early embryogenesis and phenotypic features. We have therefore studied the early post-implantation stages of development of spontaneously occurring digynic triploid mouse embryos and experimentally induced diandric and digynic triploids, as well as diandric heterozygous diploids and homozygous tetraploid embryos. This material has been examined morphologically and cytogenetically, in order to investigate whether any relationship exists between their phenotype, genotype and developmental potential. Attention is drawn to the fact that the detailed analysis of this material has already shed important new light on the genetic factors that influence early mammalian development. In addition, it appears likely that it has the potential to provide new insights into pattern formation, in particular in relation to the craniofacial region, the heart and the post-cranial vertebral axis.