Equivalence of the total constitutive heterochromatin content by an interchromosomal compensation in the C band sizes of chromosomes 1, 9, 16, and Y in Caucasian and Japanese individuals.

A quantitative analysis of C bands by densitometric measurements in chromosomes 1, 9, 16, and Y was conducted in Caucasians and Japanese living in Brazil. Sixty normal unrelated subjects (30 males and 30 females) were studied in each racial group. Caucasians presented C bands of chromosomes 1, 9, and 16 larger than Japanese, but, on average, only the difference for C bands of chromosome 9 was statistically significant. In the Japanese, the C band sizes of chromosomes Y were, on average, significantly larger than in the Caucasians. The mean C band size of chromosome 9 and the sum of the three pairs were significantly larger in Caucasian than in Japanese males. The total values of constitutive heterochromatin, sigma (1qh,9qh,16qh,Yq12), did not show significant difference between Caucasian and Japanese males. The relative C band sizes of chromosomes 1, 9, and 16 were, on average, similar in Caucasians and Japanese. No sex difference was found in both racial groups. As regards the heteromorphism, only the values of C bands of chromosome 9 were, on average, significantly larger in Caucasians than in Japanese. Partial inversions were detected only among the Caucasians.