Distinct clustering of mitochondrial DNA types among Japanese, Caucasians and Negroes

Analysis of the data for mitochondrial DNA using restriction enzymes revealed a total of 117 different types among Japanese, Caucasians and Negroes. The average number of nucleotide substitutions for the Japanese was almost the same as that for the Caucasians, whereas the value for the Negroes was almost two times larger than those for the other two races. A phylogenetic tree constructed by genetic distances showed distinct clusters of individuals from the same racial group, although there were intermin-glings of individuals from different racial groups in some clusters. The overall clustering pattern in the tree suggested that the ancestral human population was already polymorphic in the mitochondrial genome before the divergence of the three major races.