Question

Sickle cell disease is caused by a mutation in the β-globin gene. Although this may be one of the most common globin gene variants, it is not the only one. Approximately how many different alleles of the human α- and β-globin genes have been documented worldwide?

Answer 1

There are over 1,000 documented alleles of the human α- and β-globin genes worldwide, which result in various forms of hemoglobin disorders including sickle cell anemia and β-thalassemia.

Step-by-step explanation:

Sickle cell disease is caused by a mutation in the β-globin gene, leading to the production of abnormally shaped hemoglobin in red blood cells, causing them to take on a sickle or crescent shape. Although sickle cell anemia is one of the common hemoglobin disorders, there are many different mutations possible in the human α- and β-globin genes. In fact, for β-thalassemia, another blood disorder, mutations can occur at eight or more sites within the β-globin gene. The number of documented globin gene variants is substantial. Worldwide, there have been over 1,000 alleles of the human α- and β-globin genes identified.

These genetic variations have significant implications for health. For example, individuals with sickle cell trait (heterozygous for the sickle cell mutation) are generally unaffected, as they produce both normal and sickle hemoglobin. However, individuals homozygous for the mutation suffer from sickle cell anemia with more severe symptoms. The prevalence of sickle cell gene variants is particularly high among populations in Africa and among African Americans due to the protective effect against malaria.