Sickle cell anaemia is an example of

Options

A. Epistasis
B. Codominance
C. Pleiotropy
D. Incomplete dominance

Answer

**Step-by-Step Solution:**

1. **Understanding Sickle Cell Anemia**: Sickle cell anemia is a genetic disorder that affects the shape and function of red blood cells (RBCs). In this condition, the RBCs become rigid and shaped like a sickle or crescent, which leads to various health issues, including anemia and reduced oxygen supply to tissues.

2. **Identifying the Genetic Basis**: Sickle cell anemia is caused by a mutation in the hemoglobin gene (HBB) on chromosome 11. This mutation leads to the production of abnormal hemoglobin (hemoglobin S), which causes the red blood cells to deform.

3. **Exploring Genetic Concepts**: To classify sickle cell anemia, we need to understand the genetic concepts involved:
- **Epistasis**: Interaction between genes where one gene masks the effect of another.
- **Co-dominance**: A situation where both alleles in a heterozygote are fully expressed.
- **Incomplete dominance**: A situation where the phenotype of the heterozygote is intermediate between the two homozygotes.
- **Pleiotropy**: A single gene influencing multiple phenotypic traits.

4. **Analyzing the Options**:
- **Option A (Epistasis)**: Incorrect, as sickle cell anemia does not involve gene masking.
- **Option B (Co-dominance)**: Incorrect, as sickle cell anemia does not show both alleles being expressed equally.
- **Option C (Pleiotropy)**: Correct, as the sickle cell mutation affects multiple traits, including pain episodes, organ damage, and susceptibility to infections.
- **Option D (Incomplete dominance)**: Incorrect, as the phenotype is not an intermediate form but rather a distinct sickle shape.

5. **Conclusion**: Based on the analysis, sickle cell anemia is best classified as an example of **pleiotropy** because the mutation affects multiple unrelated phenotypic traits.

**Final Answer**: Sickle cell anemia is an example of **pleiotropy**.

---