HBB and sickle cell disease: Among the missense DMs, Xue et al. (2012) identified known pathological variants such as HBB (c.20A>T; p.Glu7Val), which leads to increased resistance to malaria in heterozygotes but to sickle cell disease in homozygotes [confined to Africans (Yoruba, YRI) in whom there were 12 heterozygotes and 1 homozygote].