Estimation of cases with dominant inheritance I am reading [1] and I didn't understand this passage: > All bilateral cases should be counted as hereditary because the proportion of affected offspring closely approximates the 50% expected with dominant inheritance. Shouldn't the percentage be 75% with dominant inheritance? [1]: Knudson, Alfred G. "Mutation and cancer: statistical study of retinoblastoma." Proceedings of the National Academy of Sciences 68.4 (1971): 820-823.

It depends on the genotype of P (parents). If only one parent carries the dominant allele, F1 will have the allele 50%.

D = dominant allele, d = recessive allele

P: dd x Dd

F1: Dd 50%, dd 50%