Question

There are 64 types of codons in genetic code dictionary because

• A. There are 64 types of tRNA's found in cell.
• B. There are 44 meaningless and 20 codons for amino acids.
• C. There are 64 amino acids for coding.
• D. Genetic code is triplet.

Answer 1

The correct option is D Genetic code is triplet.

The genetic code is a triplet and this triplet nature can be explained as:

• There are four nitrogenous bases (Adenine, Guanine, Thymine and Cytosine) and these four bases code for 20 amino acids.
• If genetic code is a doublet then a combination of two nitrogenous bases will give 4 x 4 = 16 codons, which is insufficient for 20 amino acids.
• George Gamow in 1954 explained the possibility of three letter code i.e. triplet codon. This will give 4 x 4 x 4 = 64 codons, which is more than enough to code for twenty amino acids.
  

Hence, the genetic code is a triplet.

So, the correct answer is 'Genetic code is triplet'.