High frequencies and grade expressions of Carabelli's trait in a sample ofthe Croatian population

Although it is generally accepted that Europeans exhibit the highest freque ncies of Carabelli's trait (70-90%), these values represent the expression of all possible morphological grades. When only a well-defined trait expres sion is considered (grades 5th, 6th and 7th), the frequency is much lower, not more than 19.2% for the 5th grade, and significantly less for the 6(th) and 7th grades. Our observations based on the study of the Croatian (Centr al European) populations show the highest frequencies for grade of the trai t (exceeding 23%). Comparative data for European or European derived popula tions demonstrate significant variation in grade expression. While the prev iously published data suggest that the highest grade of the trait expressio n does not exceed 10%, our figures show the highest yet known frequency of a well-defined trait.