Question

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.
A. Statement I is incorrect but statement II is true
B. Statement I and statement II are true
C. Statement I and statement II are false
D. Statement I is correct but statement II is false

Answer 1

The 'AUG' codon codes only for methionine and serves as the initiation codon for protein synthesis, while the codons 'AAA' and 'AAG' both code for lysine. Therefore, the answer is A. Statement I is incorrect but statement II is true.

Step-by-step explanation:

In the context of genetic codes and protein synthesis, Statement I claims that the codon 'AUG' codes for both methionine and phenylalanine, which is incorrect. 'AUG' is known to serve a dual role as the initiation codon, always initiating protein synthesis by coding for methionine, and it does not code for phenylalanine. Therefore, this single codon initiates the synthesis of a polypeptide and only codes for methionine.

Statement II states that both 'AAA' and 'AAG' codons code for the amino acid lysine, which is correct. Given the degeneracy of the genetic code, these two codons are among those that code for the same amino acid - lysine.

Hence, the correct answer to the question is A. Statement I is incorrect but statement II is true.