Whether any such advantage is exclusive to heterozygous female individuals, or whether it is shared by both sexes equally has been especially controversial.4, 18 Many factors might account for these apparently conflicting conclusions, including small sample sizes, variations in study design and malaria outcomes, inconsistent definitions for G6PD deficiency (including those based on both biochemical and genetic methods), allelic heterogeneity at the G6PD locus, and epistatic interactions between G6PD deficiency and polymophisms at other loci. The gene discussed is G6PD; the disease is G6PD deficiency.