Incidence of cleft lip and palate in British Columbia Indians.

It is generally recognized that there is a genetic component in the cleft lip and cleft palate malformation in man. There is good evidence that this malformation is heterogeneous, and that parts of it, for example isolated cleft palate compared with cleft lip with or without cleft palate, may have different genetic origins. The types of genetic mechanisms postulated for these defects have included both major gene (autosomal dominant and recessive) and polygenic effects (Carter, 1965). Empirical risk figures derived from family studies are in reasonably good agreement with a polygenic genetic system. These empirical risk figures have a practical value in the provision ofgenetic counselling advice to families in which these defects have occurred. To date, family studies have been confined almost exclusively to Caucasian populations, and hence the recurrence risks derived from such studies are not applicable directly to non-Caucasian populations. As part of