In beta-thalassemia, two genetic mutations lead to which condition?

• A. Thalassemia major/Cooley's anaemia
• B. Beta-thalassemia minor
• C. Sickle cell disease
• D. Alpha-thalassemia

Answer: (A)

When both copies of the beta-globin gene are mutated, you get beta-thalassemia major. This form is severe because beta-globin production is greatly reduced or absent, since the mutations are present on both alleles. The condition is inherited in an autosomal recessive pattern, so a person must receive a mutated gene from each parent to develop it.

For contrast, having one mutated beta-globin gene causes beta-thalassemia trait (minor) with mild anemia, not the severe disease. Sickle cell disease is caused by a different mutation in the beta-globin gene that leads to hemoglobin S, not by two beta-thal mutations. Alpha-thalassemia involves deletions or mutations in the alpha-globin genes, a separate set of genes from beta-globin.

So, two genetic mutations in the beta-globin gene specifically lead to beta-thalassemia major, also known as Cooley’s anemia.