Segregation and transmission of chromosomes from a reciprocal translocation in Gallus domesticus cockerels

Segregation behavior of a reciprocal translocation involving the long arm of chromosome No. 1 and a microchromosome was studied in secondary spermatocytes and embryos produced by heterozygous cockerels. The types and frequencies of the various balanced and unbalanced chromosome complements were determined. Complementary products of segregation did not occur in the expected ratios of 1:1 in secondary spermatocytes. The excess of spermatocytes with deficiency of the long arm and duplication of the short arm might be the result of lagging of the long arm at meiosis I, the centromere of the long arm being derived from a microchromosome. In the samples of secondary spermatocytes and embryos 52.5% and 49.6%, respectively, contained balanced chromosome complements. A significantly higher proportion of duplications and deletions of the long arm was seen in embryos than in secondary spermatocytes. Conversely, a lower proportion of duplications and deletions of the short arm was seen in embryos than in secondary spermatocytes. Apparently, spermatogenic cells bearing different unbalanced genomic contents are not equally viable or fertile.