Molecular Analysis of Turkish β-Thalassemia Heterozygotes with Normal Hb A₂ Levels

Abstract

Four parents of three unrelated families who are obligatory β-thalassemia heterozygotes and two parents with Hb Knossos are presented. In these subjects, although the red blood cell counts and red cell indices were compatible with β-thalassemia trait, the Hb A₂ values were between 1.9–2.9 % of the total hemoglobin. Examination of the δ-globin gene by Southern blot, restriction endonuclease analysis, and by direct sequencing of amplified DNA revealed the presence of the (δ˚) -7.2 kb Corfu type deletion, the (δ⁺) codon 27 (G→T) and (δ˚) IVS-I-2 (T→C) mutations in trans or in cis with a severe β-thalassemia allele, and the (δ˚) codon 59 (-A) deletion in cis with the β^Knossos allele.