Sickle-cell anaemia is caused by a substitution mutation. At this sixth position of haemoglobin, ………... due to this mutation

Options

A. basic amino acid is replaced by acidic amino acid
B. acidic amino acid is replaced by basic amino acid
C. acidic amino acid is replaced by acidic amino acid
D. acidic amino acid is replaced by neutral amino acid

Answer

To solve the question regarding sickle-cell anemia and the substitution mutation at the sixth position of hemoglobin, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Sickle-Cell Anemia**:
- Sickle-cell anemia is a genetic disorder caused by a mutation in the hemoglobin gene. This mutation is specifically a substitution mutation.

2. **Identifying the Mutation**:
- The mutation occurs at the sixth position of the beta-globin chain of hemoglobin. In normal hemoglobin, the codon at this position is GAG, which codes for glutamic acid (an acidic amino acid).

3. **Analyzing the Change**:
- In sickle-cell hemoglobin, the codon changes from GAG to GUG due to a single nucleotide substitution. GUG codes for valine, which is a neutral amino acid.

4. **Determining the Type of Amino Acid Replacement**:
- Therefore, the mutation results in the replacement of glutamic acid (acidic) with valine (neutral). This change is significant as it alters the properties of the hemoglobin molecule, leading to the sickling of red blood cells.

5. **Conclusion**:
- The correct statement to fill in the blank is: "At this sixth position of hemoglobin, glutamic acid is replaced by valine due to this mutation."

### Final Answer:
At this sixth position of hemoglobin, glutamic acid is replaced by valine due to this mutation.

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