In a polypeptide chain of 125 amino acids, if the `25^(th)` amino acid is mutated to UAA, then :-

Options

A. A polypeptide of 124 amino acid is formed
B. A polypeptide of 25 amino acid is formed
C. A polypeptide of 24 amino acid is formed
D. Any of the above can be possibel

Answer

To solve the question regarding the mutation of the 25th amino acid in a polypeptide chain of 125 amino acids to UAA, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Polypeptide Chain**:
- A polypeptide chain is made up of amino acids linked together. In this case, the chain consists of 125 amino acids.

2. **Identifying the Mutation**:
- The question states that the 25th amino acid is mutated to UAA. UAA is one of the three stop codons (along with UAG and UGA) that signal the termination of protein synthesis.

3. **Role of Stop Codons**:
- Stop codons do not code for any amino acids. When a ribosome encounters a stop codon during translation, it halts the addition of further amino acids to the growing polypeptide chain.

4. **Effect of the Mutation**:
- Since the 25th amino acid is mutated to UAA, the translation process will stop at this point. This means that no further amino acids will be added beyond the 24th position.

5. **Conclusion**:
- As a result of this mutation, the polypeptide chain will consist of only 24 amino acids, as the translation will terminate prematurely at the 25th position due to the presence of the stop codon UAA.

### Final Answer:
- A polypeptide of 24 amino acids will be formed.

---