Sickle cell anaemia is an example of

Options

A. Sex linked inheritance
B. Autosomal heritable disease
C. Infectious disease
D. Deficiency disease

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. Instead of being round and flexible, the red blood cells become rigid and shaped like a sickle or crescent.

2. **Identifying the Cause**: The condition is caused by a point mutation in the hemoglobin gene (specifically in the beta chain of hemoglobin). This mutation leads to the production of abnormal hemoglobin, known as hemoglobin S (HbS).

3. **Inheritance Pattern**: Sickle cell anemia is inherited in an autosomal recessive manner. This means that an individual must inherit two copies of the mutated gene (one from each parent) to exhibit the disease. If an individual has one normal gene and one mutated gene, they are considered a carrier (heterozygous) but typically do not show symptoms.

4. **Resistance to Malaria**: Individuals who are heterozygous (HbA/HbS) for the sickle cell trait have a survival advantage in regions where malaria is prevalent. This is because the presence of the sickle cell trait provides some resistance to malaria, which is why the trait is more common in these areas.

5. **Conclusion**: Given that sickle cell anemia is a heritable condition that is passed down through generations and is caused by a mutation in an autosomal gene, it is classified as an **autosomal heritable disease**.

### Final Answer:
Sickle cell anemia is an example of **autosomal heritable disease** (Option 2).

---