EVIDENCE FOR A MAJOR GENE IN THE SUSCEPTI BILITY TO CLEFT LIP PALATE - SEGREGATION ANALYSIS IN THE CHILEAN POPULATION/

The most generally accepted model for cleft lip/palate not associated to specific syndromes has been the one that postulates multifactorial inheritance with a threshold. Recent studies using complex analytical techniques have suggested the existence of a major gene with decreased penetrance in its etiology. Some authors have postulated that only a fraction of all cases of non-syndronmic CL (P) would be explained by a single major gene. Other cases may be due to different genes, to envi ronmental agents or to the interaction between them. The present study tests the monogenic inheritance model for CL (P) using segregation an alysis in a sample of 211 extended pedigrees collected through CL (P) affected probands. The hypotheses of an autoscmic recessive gene was a nalized in 151 sibships (size 2 or more) using ''Apert's'' method, ''m aximum likelihood method'', ''singles method'' and ''sib's, method'' ( single incomplete ascertainment). Results obtained do not support the hypotheses of autosomal recessive inheritance. Instead, the hypothesis of an autosomal dominant mode of inheritance with low penetrance is n ot rejected when analyzing the proportion of normal and affected proge ny in certain types of matings in a subsample of 30 extended pedigrees with two or more affected individuals.