Constitutive heterochromatin distribution in pig ( Sus scrofa) chromosomes.

Constitutive heterochromatin (HC = C-banding) distribution was studied in pig (Sus5crofa) chromosomes from 20 animals belonging toCinta Senese and Calabrese breeds raised in southern Italy. The use of CBG-banding, sequential GBG/CBA-banding and sequential GBG/Ag-NOR/CBA-banding techniques allowed more detailed characterization of C-banding patterns in pig chromosomes (SSC). The following features were noticed: (a) all autosomes and the X-chromosome showed centromeric C-positive bands; (b) the entire q-arm and proximal part of the p-arm y chromosome were C-positive: (c) clear interstitial C-positive bands were noticed in SSC1q17, SSC3p14 and SSC16q21; (d) the nucleolus organizer (NO) chromosome 10 showed two distinct HC-blocks very far apart in both arms with large, polymorphic (different size) NORs between the chromosome pair, while NO-chromosome 8 showed only one C-positive band (the smallest) in the q-arms; (e) C-band polymorphism was observed between and within chromosome pairs also in related subjects (three generations were followed); (f) the C-banding patterns are inherited in Mendelian fashion; (g) the most common C-band polymorphic chromosomes pairs were SSC 1, 7, 9, 11, 12, 16,17 and 18.