**Core Concept**
Alpha thalassemia is a genetic disorder caused by the deletion or mutation of one or more of the four alpha-globin genes located on chromosome 16. This condition leads to reduced or absent production of the alpha-globin chains, which are essential for the production of hemoglobin A, the main oxygen-carrying protein in red blood cells.

**Why the Correct Answer is Right**
The correct answer is related to the deletion of the alpha-globin genes. This deletion leads to the production of abnormal hemoglobin chains, causing an imbalance in the production of alpha-globin chains compared to beta-globin chains. As a result, the production of hemoglobin A is reduced, and the production of hemoglobin H, a tetramer of four alpha-globin chains, is increased. This imbalance causes the symptoms of alpha thalassemia, including anemia, jaundice, and bone deformities.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the genetic mechanism behind alpha thalassemia. While mutations in the alpha-globin genes can cause the condition, the question specifically asks for the cause of alpha thalassemia.
**Option B:** This option is incorrect because it refers to beta thalassemia, a different genetic disorder caused by mutations in the beta-globin genes.
**Option C:** This option is incorrect because it refers to a different genetic disorder altogether.

**Clinical Pearl / High-Yield Fact**
It's essential to note that alpha thalassemia is more common in individuals of Mediterranean, Middle Eastern, and Southeast Asian descent, where the deletion of one or more alpha-globin genes is a common genetic trait.

**Correct Answer: D**