Question:
Which of the following is true about the start codon in the genetic code dictionary ?
Which of the following is true about the start codon in the genetic code dictionary ?
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The universal start codon is AUG, coding for Methionine.
In rare bacterial cases, GUG or UUG can act as alternative start codons, but they still recruit initiator tRNA-methionine during initiation, meaning the first amino acid remains methionine.
In rare bacterial cases, GUG or UUG can act as alternative start codons, but they still recruit initiator tRNA-methionine during initiation, meaning the first amino acid remains methionine.
Updated On: Jul 23, 2026
- It is the same as one of the stop codons.
- It codes primarily for the amino acid methionine.
- The codon is UAG.
- It codes for the amino acid valine.
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Concept:
The genetic code is the set of rules used by living cells to translate information encoded within genetic material (DNA or mRNA) into proteins.
It consists of 64 triplet codons, including start (initiation) and stop (termination) codons.
Step 2: Detailed Explanation:
Let us analyze the properties of the start codon in translation:
The universal start codon is AUG.
During translation initiation, the ribosome identifies this codon on the mRNA to establish the reading frame and begin protein synthesis.
The codon AUG codes specifically for the amino acid Methionine (specifically, N-formylmethionine in prokaryotes, and standard methionine in eukaryotes).
Therefore, almost all newly synthesized polypeptide chains begin with methionine as their first amino acid, which matches Option (B).
The three stop codons are UAA (Ochre), UAG (Amber), and UGA (Opal).
These do not code for any amino acids and signal the termination of translation, which excludes Options (A) and (C).
The codons for Valine are GUU, GUC, GUA, and GUG, which excludes Option (D).
Step 3: Final Answer:
The start codon codes primarily for the amino acid methionine.
This corresponds to Option (B).
The genetic code is the set of rules used by living cells to translate information encoded within genetic material (DNA or mRNA) into proteins.
It consists of 64 triplet codons, including start (initiation) and stop (termination) codons.
Step 2: Detailed Explanation:
Let us analyze the properties of the start codon in translation:
The universal start codon is AUG.
During translation initiation, the ribosome identifies this codon on the mRNA to establish the reading frame and begin protein synthesis.
The codon AUG codes specifically for the amino acid Methionine (specifically, N-formylmethionine in prokaryotes, and standard methionine in eukaryotes).
Therefore, almost all newly synthesized polypeptide chains begin with methionine as their first amino acid, which matches Option (B).
The three stop codons are UAA (Ochre), UAG (Amber), and UGA (Opal).
These do not code for any amino acids and signal the termination of translation, which excludes Options (A) and (C).
The codons for Valine are GUU, GUC, GUA, and GUG, which excludes Option (D).
Step 3: Final Answer:
The start codon codes primarily for the amino acid methionine.
This corresponds to Option (B).
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