The nucleotide sequence of a gene's DNA specifies the amino acid sequence of a protein through the genetic code. Sets of three nucleotides, known as <answer>codons</answer>, each correspond to a specific amino acid.:6 Additionally, a "start codon", and three "stop <answer>codons</answer>" indicate the beginning and end of the protein coding region. There are 64 possible <answer>codons</answer> (four possible nucleotides at each of three positions, hence 43 possible <answer>codons</answer>) and only 20 standard amino acids; hence the code is redundant and multiple <answer>codons</answer> can specify the same amino acid. The correspondence between <answer>codons</answer> and amino acids is nearly universal among all known living organisms.
What are sets of three nucleotides known as?
codons