Observe the table and answer the given question:
Identify the statements which are true with respect to the table given above.
(A) There are 64 codons coding for twenty amino acids
(B) The codon for methionine is CUG
(C) Serine and Leucine have 6 codons each coding for them
(D) UAA is a stop codon
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (C) and (D) only
(A) There are 64 codons coding for twenty amino acids — False. Only 61 codons code for amino acids; 3 are stop codons.
(B) The codon for methionine is CUG — False. Methionine is coded by AUG; CUG codes for leucine.
(C) Serine and Leucine have 6 codons each coding for them — True.
(D) UAA is a stop codon — True.
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.”