Sickle cell anaemia is induced by :

Options

A. Change of amino acid in `alpha` - chain of haemoglobin
B. Change of amino acid in `beta` - chain of haemoglobin
C. Change of amino acid in both `alpha-and beta ` - chain of haemoglobin
D. Change of amino acid in either `alpha-"or " beta ` - chain of haemoglobin

Answer

### Step-by-Step Solution:

1. **Understanding Sickle Cell Anemia**:
- Sickle cell anemia is a genetic disorder that affects the shape of red blood cells (RBCs). Instead of being round and flexible, the RBCs become rigid and shaped like a sickle or crescent.

2. **Genetic Basis**:
- This disorder is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutated gene (one from each parent) to exhibit the disease.

3. **Role of Hemoglobin**:
- Hemoglobin is a protein in red blood cells responsible for transporting oxygen. It consists of two types of chains: alpha and beta chains.

4. **Identifying the Mutation**:
- The mutation responsible for sickle cell anemia occurs specifically in the beta chain of hemoglobin.
- At the 6th position of the beta globin chain, glutamic acid (which is coded by the GAG codon) is replaced by valine (which is coded by the GUG codon) due to a point mutation.

5. **Impact of the Mutation**:
- This single amino acid substitution (from glutamic acid to valine) leads to the distortion of the red blood cell shape, causing them to become sickle-shaped. This affects their ability to carry oxygen effectively.

6. **Conclusion**:
- Based on the information provided, the correct answer to the question "Sickle cell anemia is induced by" is the "change of amino acid in the beta chain of hemoglobin."

### Final Answer:
**Change of amino acid in beta chain of hemoglobin.**

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