Abstract
An extended survey of 8,103 Sardinian newborns has been conducted for the study of abnormal γ-globin gene arrangements. Fetal hemoglobin analysis and globin gene mapping have identified five different arrangements in 24 babies: five (21%) were carriers of the -GAγ- hybrid (thalassemic) gene, directing the synthesis of the Aγ chain and resulting in low 641%) Gγ chain and decreased Hb F levels; two (8%) carried the -Aγ-Aγ-T- duplication, characterized by even lower (37%) Gγ levels; five (21%) carried the -Gγ-AGγ- Aγ- triplication; one (4%) carried the -Gγ-Gγ-Aγ- triplication, and 11 (46%) the -Gγ-Gγ- duplication, all resulting in high Gγ levels (85, 83, and 88%, respectively). Thirty-six additional babies could be phenotypically classified as carriers of the same mutations. Haplotyping and γ-chain composition showed that the crossover event generating the -GAγ- hybrid gene and the corresponding -Gγ-AGγ-Aγ- triplication has occurred on at least three different chromosomes. The -Gγ-Gγ- duplication was associated with the chromosome having haplotype I, and the -Aγ-Aγ-T- with the chromosome of haplotype II. As many as 2,260 babies (28%) were heterozygous, and 254 (3%) homozygous for the AγT mutation. The incidence and relative distribution of these anomalies in Sardinia are different when compared with those of other ethnic groups.