Question

Which of the following is a stop codon?

• A. AUG
• B. UGG
• C. UGA
• D. UAC

Hint:

Remember the mnemonic for stop codons: {U Are Annoying} — UAA, UAG, and UGA.

Answer 1

The Correct Option is C

To determine which of the given options is a stop codon, we need to understand the role of codons in genetic coding.

Codons: Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids or signal the termination of protein synthesis (stop codons).

In mRNA, codons consist of combinations of the four nucleotides: Adenine (A), Uracil (U), Cytosine (C), and Guanine (G). There are a total of 64 codons, of which 61 code for amino acids, and 3 are stop codons.

Stop Codons: The three stop codons in mRNA are UAA, UAG, and UGA. These stop codons signal the end of protein synthesis by preventing the addition of further amino acids.

1. AUG: This is a start codon that codes for Methionine and signals the initiation of protein synthesis. It is not a stop codon.
2. UGG: This codes for the amino acid Tryptophan. It is not a stop codon.
3. UGA: This is one of the three stop codons that signal the termination of protein synthesis. Therefore, it is a stop codon.
4. UAC: This codes for the amino acid Tyrosine. It is not a stop codon.

Based on the information above, the correct answer is UGA as it is one of the stop codons.