Since the number of pre- and postimplantation human polyploid embryos available for analysis is very small and relatively few are available at any one centre, I have used appropriate experimental mouse models to facilitate a large scale investigation. One aim was to analyse the influence of ploidy on the cleavage rate of preimplantation embryos. A deviation from the optimum embryonic (diploid fertilized) cell number during this time might explain the poor development and failure of genetically abnormal embryos. Therefore, experimentally produced haploid, diploid, triploid and tetraploid embryos were analysed together with appropriate control embryos. In addition, the analysis of parthenogenetic embryos and diandric and digynic triploid and homozygous tetraploid embryos during this time would also enable the influence of the parental genomes on development to be investigated. I also wished to examine whether a predictable relationship existed between ploidy and cell size and number in the tissues of postimplantation mammalian polyploid embryos. Confirmation of such a relationship may explain the abnormal morphological features encountered in some of these embryos and the premature death of all triploid and tetraploid mouse embryos, and the majority of human embryos with similar genetic abnormalities. My results show that the duplication of one or both parental genomes leading to the triploid or tetraploid status, respectively, still allows apparently normal preimplantation development to occur. However, the loss of a haploid genome from the diploid status is invariably detrimental to normal development. My results confirm that the presence of a maternal genome is important for normal early embryogenesis since parthenogenetic diploid embryos and diandric and digynic triploid embryos developed as well as fertilised diploid embryos during the pre- and very early postimplantation period.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:652353 |
| Date | January 1994 |
| Creators | Henery, Caroline Cecilia |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/19837 |
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