Cleft Lip and Cleft Palate: A Genetic Study

Abstract

A fundamental approach to any human hereditary problem is con— cerned with identifying those individuals in a population who carry a gene for a given affliction but who do not clearly demonstrate the described phenotype for that gene. This implies that accurate definition of phenotype must precede all other considerations. Many families diSplay a definite hereditary tendency to have cleft lip and palate individuals but do not show a specific mode of inheritance for these conditions. One reason for this discrepancy is probably an in— adequate designation and definition of the phenotype for a clefting gene or genes. Such varying phenotypes may result from either or both of the following conditions: a) minor anatomical discrepancies in the area of the lip and palate which represent modification of gene action by en— vironment or other genes in the genome, and b) genetic heterozygosity in which an individual displays minor anatomical discrepancies which designate him as a " carrier " of the gene for cleft lip and palate. The purpose of this study was to identify and to determine the prevalence of a number of orofacial variations which are possible incomplete manifestations of gene action. This would permit better definition of the phenotype of cleft lip and palate and thereby help to clarify any role these microforms might play in delineating a specific mode of inheritance. Experimental Procedure METHOD AND MATERIALS. A total of 11 families with more than a single occurrence of cleft lip with or without cleft palate, hereafter referred to as CL, CLP, and/0r isolated cleft palate, hereafter referred to as CP, was studied. A total of 138 individuals was examined, representing first and second degree relatives and first cousins of the proband. If there was at least one other affected parent, sibling, or first cousin of the proband, the family was included for study. The purpose of selecting families with such closely related affecteds was to minimize the pos— The authors are affiliated with the