CBSE 2025, Compartment, Set 1

Question

What would happen if in a gene encoding a polypeptide of 51 amino acids, codon present at 32 position (UAU) is mutated to UGA? Select the option that indicates the polypeptide with correct number of amino acids formed after mutation. A). A polypeptide of 50 amino acids will be formed. B). A polypeptide of 32 amino acids will be formed. C). Two polypeptides of 20 and 31 amino acids will be formed. D). A polypeptide of 31 amino acids will be formed.

Edvaya · Accepted Answer

The correct answer is A polypeptide of 31 amino acids will be formed.. **SOLUTION** The codon **UGA** is a universal **stop (termination) codon**. If a mutation changes the $32^{	ext{nd}}$ codon to UGA, the translation process (protein synthesis) will abruptly stop right before that position. Therefore, the ribosome will successfully translate only the first 31 codons, resulting in the formation of a truncated polypeptide containing exactly **31 amino acids**.

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Biology > Reproduction And Genetics > Molecular Basis Of Inheritance

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