Regardless of epistasis between alpha and beta thalassaemia, or any effect of SAO or G6PD, the fact that the −α/−α ββ genotype leads to microcytosis means that there is likely to be a negative correlation between alpha thalassaemia frequency and OTOFT specificity for carriers of beta thalassaemia (Fig5). The gene discussed is G6PD; the disease is alpha thalassemia spectrum.