Final answer:
Sickle cell anemia is caused by a mutation in the beta chain of hemoglobin, resulting in a single amino acid substitution. The mutation leads to the formation of sickle-shaped red blood cells, which disrupt capillary flow and oxygen delivery, causing the symptoms of anemia.
Step-by-step explanation:
Sickle cell anemia is caused by a mutation in the gene that encodes the beta chain of hemoglobin. Specifically, there is a single amino acid substitution where valine replaces glutamic acid in the beta chain. This small change in the primary structure of the protein alters its function significantly, causing red blood cells to become sickle-shaped instead of disc-shaped. The sickle-shaped cells disrupt capillary flow and oxygen delivery, resulting in the symptoms of anemia.
It is important to note that a hemoglobin molecule is made up of two alpha chains and two beta chains, with each chain consisting of about 150 amino acids. The structural difference between a normal hemoglobin molecule and a sickle cell molecule is just a single amino acid difference out of the 600 in total. This single amino acid substitution is caused by a point mutation, where one base in the gene's coding region is changed.
The mutation in the beta chain of hemoglobin leads to the formation of abnormal hemoglobin molecules, which in turn affects the shape and function of red blood cells. The sickle-shaped red blood cells are less flexible and can easily get stuck in blood vessels, leading to blocked blood flow and a range of complications associated with sickle cell anemia.