Size variability of the Y chromosome distal C-band in Brazilian Indians and Caucasoids.

Densitometric measurements of the Y chromosome distal heterochromatin were performed on 183 Indians and 21 Caucasoids living in Brazil. No significant intratribal intervillage variation was observed, but the tribal averages were different, ranging from 0.81 to 1.32 mu. The Caucasoid mean presented an intermediate value. Wide intrapopulation variability occurs, as well as a suggestion of bimodality in the measurements obtained among the Indians of the Amazon region. Surprisingly a positive correlation was found between this variable and the C-band size of chromosome 16, as well as between it and the heteromorphism index of chromosome 1.