Abstract
Recent reports (MUKAI et al. 1974; KATZand CARDELLINO1978; COCKER-HAM and MUEAI 1978) have indicated that the Cy chromosome is not always dominant over its homologous chromosome with respect to viability. Thus,the genetic parameters previously estimated using viabilities determined by the Cy method are biased. In the present paper, the biases of the estimates for the polygenic mutation rate, the degree of dominance and the homozygous load are examined. The results indicate that the biases for the mutation rate and the degree ofdominance are small and that the estimate of the homozygous load relative to the average viability of the population is not biased.