**3.13 Sickle-cell anemia**

Sickle-cell anemia is an autosomal recessive genetic disease. It results from a mutation at the sixth codon of the β hemoglobin gene on chromosome 11 (the hydrophilic amino acid glutamic acid is replaced by the hydrophobic amino acid valine). This mutation causes red blood cells to become rigid and inflexible. The patient's red blood cells are difficult to go through small capillaries, leading to stroke, chronic pain, anemia, and infection. This disease affects more than 300, 000 people worldwide (Ataga, 2009; Chang et al., 2006; Ingram, 1956, 1957; Pawliuk et al., 2001; Wu et al., 2006).
