Blastomere karyotyping and transfer of chromosomally selected embryos. Implications for the production of specific animal models and human prenatal diagnosis.

A method is described that permits the generation of four isolated blastomeres after embryo splitting of murine four-cell eggs and the subsequent chromosomal analysis of one of the obtained 1/4-blastomeres. According to the karyograms obtained, embryos can be selected for reimplantation and furthermore triplicated via the embryo splitting procedure. By employing the described experimental setup, it is possible specifically to produce trisomy 16----2n aggregation chimeras as a postnatal model system of human Down's syndrome. The design can also be used for embryo sexing in stock farming and the selective reproduction of sexed farm animals via embryo transfer. Furthermore the application of blastomere karyotyping in human genetic counseling is discussed for the descendants of carriers of Robertsonian translocations. In addition the reported method could be employed for the genotypic identification of early homozygous embryonic stages from persons carrying frequent recessive mutations. The proposed design could, therefore, widen the spectrum of prenatal diagnosis.