Assertion :- In sickle cell anaemia, the shape of RBC becomes elongated sickle like from biconcave disc.
Reason :- The mutant haemoglobin molecule undergoes polymerization under low oxygen tension causing the change in shape.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are trur but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is Flase.
D. If both Assertion & Reason are false.

Answer

**Step-by-Step Text Solution:**

1. **Understanding Sickle Cell Anemia**: Sickle cell anemia is a genetic disorder caused by a mutation in the hemoglobin gene. It is an autosomal recessive condition, meaning that an individual must inherit two copies of the mutated gene (one from each parent) to exhibit the disease.

2. **Identifying the Mutation**: The mutation responsible for sickle cell anemia occurs at a single point in the DNA sequence. Specifically, the codon GAG, which codes for the amino acid glutamic acid, is replaced by the codon GUG, which codes for the amino acid valine. This change occurs at the sixth position of the beta-globin chain of hemoglobin.

3. **Effect on Red Blood Cells (RBCs)**: Under normal conditions, red blood cells (RBCs) have a biconcave disc shape, which allows them to be flexible and efficient in transporting oxygen. However, in sickle cell anemia, the presence of the mutant hemoglobin (HbS) leads to a change in the shape of the RBCs.

4. **Polymerization Under Low Oxygen Tension**: When oxygen levels are low, the mutant hemoglobin molecules (HbS) undergo polymerization. This means that the hemoglobin molecules stick together, forming long, rigid structures that distort the shape of the RBCs from the normal biconcave disc to an elongated, sickle-like shape.

5. **Conclusion of Assertion and Reason**: The assertion states that in sickle cell anemia, the shape of RBCs becomes elongated and sickle-like, which is true. The reason provided explains that this shape change is due to the polymerization of the mutant hemoglobin under low oxygen tension, which is also true. Therefore, both the assertion and reason are correct, and the reason correctly explains the assertion.

6. **Final Answer**: Since both statements are true and the reason is a correct explanation of the assertion, the correct answer is option one.

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