An inherited, autosomal recessive disease that affects approximately 1 out of 400 African Americans. Caused by a mutation in amino acid #6 of the Hemoglobin beta chain from Glutamic acid to Valine. It is surmised that this mutation persisted in the population because the heterozygote state (no symptoms) confers a resistance to malaria. The actual cause of the disease was first discovered by Linus Pauling, a discovery for which he won the Nobel Prizes: Chemistry in 1954. This mutation causes the red blood cells to "sickle" into a crescent shape in conditions of low oxygen or dehydration. These misshapen blood cells can block blood vessels, causing extreme pain, swelling, jaundice, and organ/central nervous system damage. It can also lead to hemolytic crisis, where red blood cells are destroyed, and aplastic crises, where the bone marrow ceases to produce blood cells. There is currently no cure, prenatal screening is recommended for couples at risk.