How many total codons are there in the genetic code?

How many total codons are there in the genetic code?

• A. 20
• B. 64
• C. 4
• D. 256

Answer: (B)

A codon is a set of three nucleotides, and there are four nucleotides to choose from at each position. So the number of possible codons is 4 × 4 × 4 = 64. These 64 codons include the ones that code for amino acids and the stop signals that end translation. While there are 20 standard amino acids, multiple codons can code for the same amino acid, and there are 3 stop codons, making a total of 64 codons in the genetic code. The other numbers don’t reflect the triplet nature of codons: 4 is just the number of nucleotides, and 256 would be 4^4.

A codon is a set of three nucleotides, and there are four nucleotides to choose from at each position. So the number of possible codons is 4 × 4 × 4 = 64. These 64 codons include the ones that code for amino acids and the stop signals that end translation. While there are 20 standard amino acids, multiple codons can code for the same amino acid, and there are 3 stop codons, making a total of 64 codons in the genetic code. The other numbers don’t reflect the triplet nature of codons: 4 is just the number of nucleotides, and 256 would be 4^4.