Sickle cell anemia is the clinical manifestation of homozygous genes for an abnormal haemoglobin molecule. The event responsible for the mutation in the Beta chain is
**Core Concept**
Sickle cell anemia is a genetic disorder caused by a mutation in the HBB gene that encodes the beta-globin subunit of hemoglobin. This mutation leads to the production of abnormal hemoglobin S (HbS), which causes red blood cells to take on a sickle shape under low oxygen conditions.
**Why the Correct Answer is Right**
The mutation responsible for sickle cell anemia is a point mutation at position 6 of the beta-globin gene, resulting in the substitution of glutamic acid with valine (Glu6Val). This mutation causes a conformational change in the hemoglobin molecule, leading to polymerization of deoxygenated hemoglobin S and the characteristic sickling of red blood cells. The mutation is a result of a genetic mutation that occurred in a single individual in West Africa thousands of years ago.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the question.
* **Option B:** This is not the correct event responsible for the mutation in the Beta chain.
* **Option D:** This option is not related to the sickle cell anemia mutation.
**Clinical Pearl / High-Yield Fact**
The sickle cell mutation is a classic example of a genetic disorder that can be transmitted in an autosomal recessive pattern, meaning that an individual must inherit two copies of the mutated gene (one from each parent) to express the disease.
**Correct Answer:** A.