The parental source of heteroploidy in chick embryos determined with chromosomally marked gametes

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Abstract
Males homozygous for chromosomal translocations were mated to karyologically normal females. The resulting embryos, after incubation for 16-18 h, were prepared for cytogenetic analysis. Of the 692 embryos analyzed, 54 (7.8%) were heteroploid or contained a major heteroploid cell line. Each of the 638 normal 2n [diploid] embryos contained 1 marker and 1 normal chromosome, indicating that none arose from gynogenesis. Thirteen homogeneous haploid [1n] embryos were identified; 24 embryos were chimeric 1n/2n and 1 was 1n/3n. All haploid cell lines contained a marker chromosome indicating androgenetic origins. The 9 homogeneous triploid (3n) embryos and the 3n cell line in a single 1n/3n embryo contained a single marker. All resulted from fertilization by single spermatozoon of eggs that were diploid as a result of suppression of the 2nd meiotic division. The 3n lines of two 2n/3n embryos were derived from other mechanisms. A single homogeneous tetraploid (4n) embryo and the 4n cell lines of three 2n/4n mosaic embryos each contained 2 marker chromosomes and presumably resulted from failure of cytokinesis in an early cleavage division.

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