How many nucleotides comprise a codon in the genetic code?

How many nucleotides comprise a codon in the genetic code?

• A. Three nucleotides
• B. One nucleotide
• C. Two nucleotides
• D. Four nucleotides

Answer: (A)

Three nucleotides. Using triplets gives 4^3 = 64 possible codons, which is enough to encode the 20 amino acids plus start and stop signals. With only two nucleotides, there would be 4^2 = 16 codons—insufficient to cover all amino acids and termination signals. If codons were four nucleotides long, there would be 4^4 = 256 possibilities, adding unnecessary complexity to the reading frame. The triplet arrangement also establishes a clear reading frame and, together with the start codon, enables consecutive, non-overlapping codons to specify amino acids (with some redundancy at the third base, known as wobble).

Three nucleotides. Using triplets gives 4^3 = 64 possible codons, which is enough to encode the 20 amino acids plus start and stop signals. With only two nucleotides, there would be 4^2 = 16 codons—insufficient to cover all amino acids and termination signals. If codons were four nucleotides long, there would be 4^4 = 256 possibilities, adding unnecessary complexity to the reading frame. The triplet arrangement also establishes a clear reading frame and, together with the start codon, enables consecutive, non-overlapping codons to specify amino acids (with some redundancy at the third base, known as wobble).