VARIABILITY OF DA DAPI AND C-HETEROCHROMATIC REGIONS - A POPULATION STUDY/

DA/DAPI and C chromosomal heteromorphic sites (1q, 9q, 15p, 16q, Yq) i n a sample of 136 unrelated individuals from the Garfagnana valley (Tu scany, Italy) have been analyzed quantitatively and qualitatively. The variations in length, between-homolog heteromorphisms, and intensity of fluorescence of the heterochromatic bands have been compared in two subsamples of the population (upper and middle valley) individualized according to geodemographic criteria. DA/DAPI heterochromatin differe d significantly from C heterochromatin, showing a lower average amount and a higher variability at each site. This suggests a differential s taining of DNA of the two banding systems. Furthermore, DA/DAPI hetero chromatin was less uniformly distributed in the population than C hete rochromatin and the regions 16q and Yq discriminated better between su bsamples. The variations of DA/DAPI fluorescence at the 15p site demon strated an excess of homomorphic individuals in the upper valley, whic h could be related to the mating structure of the population living in this area.