Quantitative analysis of C-band size in human chromosomes.

The C-bands of chromosomes 1, 9, 16 and Y of 434 individuals were measured using densitometry. The regression coefficients observed between the length of these regions and that of lq-h varied between 0.046 and 0.189, showing a clear size effect (the larger the band, the higher the contraction per unit size). Negative regressions between the band sizes of the autosomes and the time that elapsed between fixation and band induction were also observed as well as an effect of the treatment (in average, the CBG-bands were 17% larger than the CNG ones). Appropriate methods were developed to correct for these factors. Despite that, correlations between the heterochromatic regions of chromosomes 1, 9 and 16 remained significantly positive (0.15-0.24). The y distal heterochromatin showed the same rate of contraction as the others. But it was not influenced by the slide's age or the different methods of band induction. It showed no relationship, after correction, with the C-bands of chromosomes 1 and 9, but the correlation with those of chromosomes 16 remained positive (0.25 and 0.26).