DNA polymorphisms in north Sardinian newborns and their linkage with abnormal ? globin gene arrangements and with ?o-thalassemia

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Abstract
Fetal hemoglobin analysis and globin gene mapping have identified one type of βo-thalassemia and four different γ globin gene arrangements among newborn babies from the northern part of Sardinia. The βo-thalassemia with a nonsense mutation at codon 39 was found on two chromosomes, each with a distinct pattern of polymorphic restriction sites; one had the AγT (Aγ75 Ile → Thr) mutation, while the second did not. Four closely related haplotypes were identified for chromosomes with the AγT mutation. The γ-thalassemia heterozygosity with the —GAγ— hybrid gene fell into two categories. One apparently originated through crossing-over between mismatched chromosomes characterized by the most common haplotype, while the other had polymorphisms resembling those of a less frequently occurring chromosome. Chromosomes with the —Gγ—AGγ—Aγ— triplication had polymorphic sites to be expected for this condition, being complimentary to the —GAγ— thalassemias. Of the two additional γ globin gene variations the —Gγ—Gγ— arrangement was associated with the chromosome with the most commonly occurring haplotype, while the chromosome with the —Aγ—Aγ— arrangement had a haplotype characteristic for that with the AγT mutation, which identified an —Aγ—AγT— arrangement. The incidental discovery of a silent β-chain mutant, Hb Hamilton, with the Val → Ile substitution at position β11, in five newborns was also reported.