Some genetic aspects of familial multiple polyposis of the colon in a kindred of 1,422 members

Summary

Genetic analysis of the kindred in this presentation indicates that the polyposis gene was transmitted as a simple mendelian dominant trait. The data showed no significant deviation from the hypothesis that the sexes are equally affected in polyposis; however, affected fathers produced a slight excess of affected sons, while affected mothers produced a marked excess of affected daughters which approached the P 0.05 level of significance. The incidence at birth of individuals with the polyposis gene was one in 6,850 for this Kentucky survey. Individuals possessing the polyposis gene had a relative biologic fitness of 84.85 per cent when compared with the general population. The penetrance of the polyposis gene in the kindred at the time of the investigation was 49.43 per cent. The mutation rate for the polyposis locus was 12 mutations per million loci per generation. Possible sources of error and bias entering into the above calculations have been discussed.