Genetic analysis of triploidy in a selected line of chickens.

We investigated the pattern of inheritance of maternal meiotic errors responsible for a high frequency of triploid progeny in a selected line of chickens. For the genetic analysis, F1 and backcross populations were produced from crosses between normal diploid individuals of the triploidy line and a control line. Triploid embryos were produced by 35% and 67% of reciprocal F1 females and by 24% and 67% of reciprocal backcross females. These results exclude autosomal recessive and sex-linked recessive or sex-linked dominant inheritance. A single autosomal dominant gene is also not likely to be responsible. However, the results are consistent with the determination of triploidy by a single autosomal gene with no dominance, and an even better fit is obtained by two loci, an autosomal gene with no dominance and a sex-linked gene. The results cannot exclude a multifactorial mode of inheritance, but the rapid response to selection for triploidy and consistent expression of the meiotic errors in different genotypes suggest that meiotic mutations at one or two loci are the most plausible genetic basis for the trait.