Sickle cell anamia is caused by substitution of sixth position

Options

A. Valine by glutamic acid in `alpha`-chain of Hb
B. Valine by glutamic acid in `beta`- chain of Hb
C. Glutamic acid by valine in `alpha`-chain of Hb
D. Glutamic acid by valine in `beta`- chain of Hb

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. It is caused by a mutation in the hemoglobin gene.

2. **Identifying the Mutation**: The specific mutation responsible for sickle cell anemia occurs at the sixth position of the beta chain of hemoglobin. This position is crucial because it determines the properties of the hemoglobin molecule.

3. **Analyzing the Amino Acid Substitution**: In normal hemoglobin, the sixth amino acid is glutamic acid. In sickle cell anemia, this glutamic acid is substituted with valine due to a single nucleotide change in the DNA sequence.

4. **Determining the Correct Option**: Given the options:
- Valine by glutamic acid in alpha chain of hemoglobin
- Valine by glutamic acid in beta chain of hemoglobin
- Glutamic acid by valine in alpha chain of hemoglobin
- Glutamic acid by valine in beta chain of hemoglobin

The correct answer is "Glutamic acid by valine in beta chain of hemoglobin" because that accurately describes the mutation leading to sickle cell anemia.

5. **Conclusion**: The mutation that causes sickle cell anemia is the substitution of glutamic acid with valine at the sixth position of the beta chain of hemoglobin.

**Final Answer**: Glutamic acid is replaced by valine in the beta chain of hemoglobin.

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