Which of the following are not correct for genetic code?
(A) The code is degenerate
(B) The codon is triplet. There are 64 codons which code for amino acids
(C) The codon is read in a contiguous fashion
(D) The code AUG has dual functions. It codes for methionine and also acts as terminator code
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (B) and (D) only
(A) The code is degenerate — Correct statement.
(B) The codon is triplet. There are 64 codons which code for amino acids — Not correct. 61 codons code for amino acids; 3 are stop codons.
(C) The codon is read in a contiguous fashion — Correct statement.
(D) The code AUG has dual functions. It codes for methionine and also acts as terminator code — Not correct. AUG acts as the initiator codon, not a terminator.
NCERT Extract:
Genetic Code – “… (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). Some exceptions to this rule have been found in mitochondrial codons, and in some protozoans. (v) AUG has dual functions. It codes for Methionine (met), and it also act as initiator codon. (vi) UAA, UAG, UGA are stop terminator codons.”