Which of the following statements about the genetic code is incorrect?

The correct answer is Option (2) → Some amino acids are coded by more than one codon, hence the code is universal.

NCERT lists the salient features of the genetic code: the codon is a triplet, the code is degenerate, it is read in a contiguous fashion without punctuation, it is nearly universal, and AUG has dual functions. Degenerate means that some amino acids are coded by more than one codon.

Option (1) The codon is triplet. — A correct statement. Each codon is made of three bases.

Option (2) Some amino acids are coded by more than one codon, hence the code is universal. — An incorrect statement. When some amino acids are coded by more than one codon, the code is called degenerate, not universal. Universal refers to the same codon coding for the same amino acid in different organisms, which is a different feature.

Option (3) The codon is read in mRNA in a contiguous fashion. — A correct statement. The codons are read one after another with no gaps or punctuation.

Option (4) The code is nearly universal. — A correct statement. From bacteria to human, UUU codes for phenylalanine; a few exceptions exist in mitochondria and some protozoans, so the code is nearly universal.

NCERT Extract:
Genetic Code – “… The salient features of genetic code are as follows: (i) 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. (ii) Some amino acids are coded by more than one codon, hence the code is degenerate. (iii) The codon is read in mRNA in a contiguous fashion. There are no punctuations. (iv) The code is nearly universal: for example, from bacteria to human UUU would code for Phenylalanine (phe).”