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 what stop codons are and their importance in genetic coding.

A stop codon is a nucleotide triplet within messenger RNA that signals the termination of translation. In genetic coding, stop codons mark the end of a protein-coding sequence. In the universal genetic code, there are three stop codons:

• UAG, known as "amber"
• UGA, known as "opal" or "umber"
• UAA, known as "ochre"

Now, let's evaluate each option against the list of stop codons:

1. AUG: This is not a stop codon. It is the start codon that also codes for the amino acid methionine.
2. UGG: This is not a stop codon. It codes for the amino acid tryptophan.
3. UGA: This is a stop codon known as "opal" or "umber," which signals the termination of protein synthesis.
4. UAC: This is not a stop codon. It codes for the amino acid tyrosine.

Therefore, the correct answer is UGA, as it is one of the three known stop codons used to terminate protein synthesis in the genetic code.

Answer 2

Step 1: Understanding codons.
A codon is a sequence of three nucleotides present on mRNA that codes for a specific amino acid or signals the termination of protein synthesis. Codons are read during the process of translation.
Step 2: Identifying stop codons.
In the genetic code, there are three stop codons that do not code for any amino acid. These stop codons signal the end of translation. The three stop codons are:
UAA, UAG, and UGA.
Step 3: Analysis of the given options.
(A) AUG: This is the start codon and codes for the amino acid Methionine.
(B) UGG: This codon codes for the amino acid Tryptophan.
(C) UGA: This is a stop codon and signals termination of protein synthesis.
(D) UAC: This codon codes for the amino acid Tyrosine.
Step 4: Conclusion.
Among the given options, UGA is the correct stop codon that terminates translation.