Question

What would happen if in a gene encoding apolypeptide of $50$ amino acids has UAC at $25^{th}$ position mutated to UAA ?

• A. A polypeptide of 25 amino acids will be formed
• B. A polypeptide of 24 amino acids will be formed
• C. A polypeptide of 49 amino acids will be formed
• D. Two polypeptides of 24 and 25 amino acids will be formed

Answer 1

Answer: (B)

UGA, UAG and UAA are three non sense (or termination) codon which do not code for any amino acid. If in a gene encoding a polypeptide of 50 amino acid, 25lh codon is mutated to UAA or any of the termination codon, then the chain will be terminated at that place because it will become difficult for /RNA to bring amino acid from amino acid pool. So in that case a polypeptide of 24 amino acid will be formed.