Which one of the following is a nonsense codon in universal code?

Question

Accepted Answer

Option 1, UAG, is the correct answer because it is one of the three nonsense codons in the universal genetic code. Nonsense codons, also known as stop codons, signal the termination of protein synthesis during translation. They do not code for any amino acids and instead instruct the ribosome to stop translating the mRNA. The three universal stop codons are UAG, UAA, and UGA. Therefore, UAG is correctly identified as a nonsense codon.

Now, let's examine why the other options are incorrect:

2. UGG: This codon is not a nonsense codon. Instead, UGG codes for the amino acid tryptophan. It is one of the 61 codons that specify amino acids and is essential for protein synthesis. Therefore, UGG cannot be considered a nonsense codon.

3. UGC: This codon codes for the amino acid cysteine. Like UGG, UGC is one of the codons that specify an amino acid and is involved in the elongation phase of protein synthesis. It is not a stop codon and thus not a nonsense codon.

4. UAC: This codon codes for the amino acid tyrosine. It is another example of a codon that specifies an amino acid, playing a role in the translation process. UAC is not a stop codon and therefore does not qualify as a nonsense codon.

In summary, Option 1, UAG, is the correct answer because it is a recognized nonsense codon in the universal genetic code, responsible for signaling the termination of protein synthesis. The other options, UGG, UGC, and UAC, are all codons that specify amino acids and are not involved in terminating translation.