Professor Endy mentions that concerns have been raised over synthetic organisms being released into the environment. One proposed solution is to insert a ‘kill switch’ into the genomes of synthetic organisms, but this solution would be ineffective if the ‘kill switch’ gene mutated. To solve this problem, synthetic biologists could create a mutation-resistant genetic code. The diagram below represents the naturally occurring genetic code, in which each set of three bases, or codon, maps to an amino acid or the end of a gene. If we were to use four bases instead of three, there would be 256 possible codons. It would then be possible to map one codon to each amino acid and leave the rest empty. This would cause the mutation of any single nucleotide to move from a mapped codon to an unmapped one, interrupting translation. Click the ‘Change’ button to see the natural genetic code turn into this mutation-resistant version.