MOLECULAR-BASIS AND HAPLOTYPE ANALYSIS OF DELTA,BETA-THALASSEMIC CHROMOSOMES IN GREECE

The molecular defect was defined in 38 delta beta-thalassemic chromoso mes from 30 unrelated heterozygous and 4 homozygous patients of Greek origin. Restriction fragment beta-gene cluster haplotypes were studies in 23 delta beta-thalassemic chromosomes. The molecular lesion was id entical in all studied cases and corresponds to the 'Sicilian' type of delta beta-thalassemia. Restriction haplotypes analysis has shown tha t, with one exception only, all Greek delta beta-thalassemic chromosom es bear the polymorphic sites which characterize haplotypes I or VII, the former being probable by indirect evidence. The striking similarit ies of the molecular lesion and the underlying haplotypes:are consiste nt with two theories: (1) The deletion occurred once on a chromosome a nd spread all over Greece and the Mediterranean area thereafter; (2) t he 5' subhaplotype +---- favors the deletional event in the delta-beta gene area.