Identify the incorrect feature of genetic code?

The correct answer is Option (4) → AUG has dual functions. It codes for Methionine and it also acts as termination codon.

The genetic code is the set of triplet codons in mRNA that decide the order of amino acids in a protein. There are 64 codons in all.

(1) The codon is triplet. 61 codons code for amino acids and 3 codons do not code for any amino acids, hence they function as stop codons. — A correct feature. The three stop codons are UAA, UAG and UGA.

(2) Some amino acids are coded by more than one codon, hence the code is degenerate. — A correct feature. Sixty-one codons are used for only 20 amino acids.

(3) The codon is read in mRNA in a contiguous fashion. There are no punctuations. — A correct feature. The codons follow one another with no gap or comma between them.

(4) AUG has dual functions. It codes for Methionine and it also acts as termination codon. — An incorrect feature. AUG has two jobs, but the second one is wrong. It codes for methionine and it is also the initiator (start) codon. It is never a stop codon.

NCERT Extract:
Genetic Code – …