The Chromosomes of Turkey Embryos during Early Stages of Parthenogenetic Development

In the early stages of parthenogenetic development in turkey eggs, many blastoderms are mosaics of haploid, diploid and polyploid cells. The genome composition of these blastoderms can be identified by C-banding. They may be generally described as either A-Z/2A-ZZ/nA-nZ or A-W/2A-WW/nA-nW and are found in a nearly 1:1 ratio. The blastoderms showing the W body (W⁺) become lethal within two days of incubation. The haploid cell proportion decreases rapidly during the early stage of development, and, as haploid cells decrease, the proportion of polyploid cells appears to increase. At six days of incubation, various kinds of parthenogenetic development can be observed. Their genome compositions are either diploid (2A-ZZ) or mosaic (A-Z/2A-ZZ). These findings suggest that diploid parthenogenesis occurs by either suppression of meiosis II or chromosome doubling some time after the first cleavage division. The frequent occurrence of mosaic blastoderms indicates that the majority, if not all, of the parthenogenetic embryos initiate their development in haploid ova.