Lethal Mutations in Brazilian Human Populations

Abstract

A SURVEY has been made in some socio-economically similar rural populations in three neighbouring townships in the southern region of the central State of Minas Gerais, Brazil. About 1,100 families of unskilled workers and a few small farmers were studied. These families have been classified according to the ethnic background of the spouses and grouped into six categories : White × White (W × W), White × Mulatoes (W × M)9 White × Negroes (W × N), Mulatoes × Mulatoes (M × M), Mulatoes × Negroes (M × N), and Negroes × Negroes (N × N). The Whites are almost exclusively of Portuguese ancestry. Within each class, families were grouped according to the coefficient of inbreeding/ of their offspring ; these values ranged as follows : 1/8, 3/32, 5/64, 9/128, 1/16, 3/64, 17/512, 1/32, 3/128, 1/64, and 0 (assumed to be non-related). A number of families where the values of/ were known to be lower than 1/64, but the precise values could not be ascertained with certainty have been discarded.