Statement I: The codon 'AUG' codes for methionine and phenylalanine.
Statement II: 'AAA' and 'AAG' both codons code for the amino acid lysine.
In the light of the above statements, choose the correct answer from the options given below.
Correct Answer :
Statement I is incorrect but Statement II is true
Solution :
The correct choice is: “Statement I is incorrect but Statement II is true”.
**Why Statement I is incorrect**
In the standard genetic code, the codon **AUG** functions as the start codon and codes for the amino acid **methionine** only. It does **not** code for phenylalanine. The amino acid phenylalanine is specified by the codons **UUU** and **UUC**. Therefore, the claim that AUG codes for both methionine and phenylalanine is false.
**Why Statement II is true**
Both codons **AAA** and **AAG** translate to the same amino acid **lysine**. This is a well‑established redundancy in the genetic code, where multiple codons can correspond to the same amino acid. Hence, the statement that AAA and AAG both code for lysine is correct.
Putting the two evaluations together, Statement I is false while Statement II is true, matching the selected answer.
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