[Chromosomal control of early mammalian development]

A review of recent studies on mammalian embryos, mostly mice, with chromosomal aberrations. Morphological, biochemical and cytological studies on mice with polyploidy, aneuploidy and some structural aberrations are discussed. Some types of chromosomal aberrations, especially monosomy for individual chromosomes (2, 5, 7, or 17), are already evident during early cleavage and are inevitably lethal by the morula stage. A direct relationship exists between the duration of survival and chromosome aberrations (trisomy and monosomy) for every chromosome. Differential gene activity of the mouse autosomes becomes evident already at the very early developmental stages. Some feasible causes of the early death of embryos with autosomal monosomy are discussed and a hypothetical mechanism for the activation of homologous autosomes at the early developmental stages is proposed. Perspectives of future studies in cytogenetics of mammalian development are outlined.