THE ORIGIN OF TRIPLOIDY IN CHICK (GALLUS DOMESTICUS) EMBRYOS

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Abstract
Cytogenetic analysis was made of 1466 chick embryos at one day of incubation. The embryos were from reciprocal crosses of two genetically diverse stocks (G1) and from matings among resulting crossbreds (G2). The overall frequency of heteroploidy was 4.6% in G1 and 5.8% in G2. The difference was not significant but the difference in frequency of triploid embryos (0.5% and 3.1%) was significant. This difference was attributed to the younger age of dams of the group with high frequency of triploidy. Furthermore, the same group of dams produced more triploid embryos when commencing their laying cycle at 19-22 weeks of age than at subsequent ages, 23-27 weeks of age, when their laying cycle had stabilized. The gonosomic complement of 54 triploid embryos was 25 ZZZ: 22 ZWW: 7 ZZW, indicating that about 80% result from failure of meiosis II of oogenesis.