**Core Concept**
Sickle cell anemia is a genetic disorder caused by a mutation in the hemoglobin gene, leading to the production of abnormal hemoglobin (HbS). This results in the formation of sickle-shaped red blood cells, which can lead to various complications. The underlying concept being tested is the molecular basis of sickle cell anemia, specifically the type of mutation that occurs.

**Why the Correct Answer is Right**
The mutation in sickle cell anemia is a point mutation that results in the substitution of glutamic acid with valine at position 6 of the beta-globin chain of hemoglobin. This substitution leads to the polymerization of deoxyhemoglobin S, causing red blood cells to sickle. The correct answer is a result of this mutation, which is an example of a **point mutation**. The **replacement** of glutamic acid with valine is a key feature of this mutation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not describe the type of mutation that occurs in sickle cell anemia. While insertions and deletions can also cause genetic disorders, they are not characteristic of sickle cell anemia.

**Option B:** This option is incorrect because it does not accurately describe the type of mutation that occurs in sickle cell anemia. While point mutations can be missense, nonsense, or silent, the replacement of glutamic acid with valine is a specific example of a missense mutation.

**Option C:** This option is incorrect because it does not describe the type of mutation that occurs in sickle cell anemia. While frameshift mutations can also cause genetic disorders, they are not characteristic of sickle cell anemia.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that sickle cell anemia is an autosomal recessive disorder, meaning that an individual must inherit two copies of the mutated gene (one from each parent) to express the disease.

**Correct Answer:** A.