Genetic Study on Cleft Lip and Palate: Test of Multifactorial Inheritance.

Family study on 591 propositi with CL/CP was performed except for 16 propositi with syndromes associated with CL/CP and multiple malformations.<BR>Results are summarized as follows;<BR>1. Affected rates in relatives of the propositi with CL(P) were 2.26% in first degree,0.37% in second degree,0.40% in third degree. The frequencies in these three degrees of relatives were about 16.2 times,2.6 times, and 2.8 times, respectively, that found in the general population.<BR>2. Affected rates in relatives of the propositi with CP were 1.64% in first degree,0.32% in second degree,0.11% in third degree. The frequencies in these three degrees of relatives were about 41.7 times,9.4 times, and 2.9 times that found in the general population.<BR>3. Affected rates in various relatives of the propositi with CL(P) and CP were similar to Edward's expected rates in polygenic inheritance, and observed relative frequencies in sibs of the propositi with CL(P) and CP were same as Penrose's expected relative frequencies in polygenic inheritance.<BR>4. In the propositi with CL(P), affected rates in three degrees of relatives of male propositi were smaller than those of female propositi. On the other hand, in the propositi with CP, affected rates in three d egrees of relatives of male propositi were larger than those of female propositi.<BR>5. Affected rates in three degrees of relatives of propositi with BCL(P) were larger than those of propositi with UCL(P). But affected rates in first and third degree of relatives of propositi with CLP were smaller than those of propositi with CL.<BR>6. In the propositi with CL(P), affected rates in first and third degree of relatives of propositi without other congenital malformations were larger than those of propositi with other congenital malformations. In the propositi with CP, there was no affected indivdual in the three degrees of relatives of propositi with oth e r congenital malformation.<BR>7. In the propositi with positive family history, affected rates in sibs were 3.9% in CL(P) propositi,14.2%in CP propositi, and those of the propositi without positive family history were 3.09% in CL(P) prop o siti,0% in CP propositi.<BR>8. In the parents of CL(P) propositi, the frequencies of contanguineous marriage in first cousins and other relative were larger than those in the general population. The frequency of first cousine marrige i n the parents of CP propositi was larger than that in the general population.<BR>9. According to Falconer's procedure, heritability of liability were estimated as 65.4±2.4% for CL(P) and 18.0±13.6% for CP.<BR>These results a re suitable for the prediction of multifactorial threshold model, so that both CL(P) and CP are polygenetic traits which are dependent on a lot of genes and enviromental factors.