HBA2 and thalassemia: We found that 16% of the healthy donors carried pathogenic hemoglobin alleles (Figure 1B), including 5 heterozygotes for hemoglobin S (HbAS), 4 heterozygotes for hemoglobin C (HbAC), and 11 individuals with one or two copies of an HBA2 deletion causing α-thalassemia (Galanello and Cao, 2011).