Final answer:
The cause of α-thalassemia is gene deletions, particularly the deletion of one or more genes responsible for the α-chain of hemoglobin. The severity of the condition is linked to the number of genes deleted which leads to an excess of β-globin chains and abnormal hemoglobin formations.
Step-by-step explanation:
The cause of α-thalassemia is primarily 1) gene deletions. In α-thalassemia, the decreased rate of synthesis of the α-chain of globin is typically due to the deletion of one or more of the four genes responsible for the α-chain in hemoglobin. A person has two pairs of α-globin genes, and the number of deleted genes impacts the severity of the disease. Deletions in these genes lead to a deficiency in the α-globin chains, causing an excess of β-globin chains. These excess β chains can form abnormal hemoglobin, such as β₄ (HbH disease), or, in more severe cases, where all four genes are deleted, (Hydrops fetalis with Hb Barts). While 2) gene mutations, 3) chromosomal abnormalities, and 4) environmental factors can contribute to various other genetic conditions, α-thalassemia is specifically caused by gene deletions.