Molecular Basis of Inheritance Question 115
115. In the genetic dictionary, there are 64 codons as
(a) 64 amino acids are to be coded
(b) 64 types of tRNAs are present
(c) there are 44 nonsense codons and 20 sense codons
(d) genetic code is triplet.
Show Answer
Answer : d
Hints & Solution
(d) Genetic code is triplet coding for one amino acid in a polypeptide chain. There are four different types of nucleotides A, U, G, and C. Since a code is a triplet thus $64(4 \times 4 \times 4)$ distinct triplet of bases determine the 20 amino acids. But out of 64 , only 61 code for 20 amino acids. Three codons that do not code for any amino acids are terminator or non sense codons (UAG, UGA and UAA). Still in 61 triplet codons there is an excess 41 codons and therefore more than one codon codes for same amino acid.
