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A comparison between the triplets tentatively deduced by these methods with the changes in amino acid sequence produced by mutation shows a fair measure of agreement.

This seems highly likely, especially as it has been shown that in several systems mutations affecting the same amino acid are extremely near together on the genetic map.

It now seems certain that the amino acid sequence of any protein is determined by the sequence of bases in some region of a particular nucleic acid molecule.

That the primary effect of gene mutation may be as simple as the substitution of a single amino acid by another and may lead to profound secondary changes in protein structure and properties has recently been strongly indicated by the work of Ingram on hemoglobin.

The balance of evidence both from the cell-free system and from the study of mutation, suggests that this does not occur at random, and that triplets coding the same amino acid may well be rather similar.

Moreover the incorporation requires the same components needed for protein synthesis, and is inhibited by the same inhibitors. Thus the system is most unlikely to be a complete artefact and is very probably closely related to genuine protein synthesis.

It is one of the more striking generalizations of biochemistry - which surprisingly is hardly ever mentioned in the biochemical textbooks - that the twenty amino acids and the four bases, are, with minor reservations, the same throughout Nature.

Mutations can arise anywhere in the genome, in gene DNA and noncoding DNA alike. But mutations to genes have bigger consequences: They can disable proteins and kill a creature.

During the decade following the discovery of the double-helical structure of DNA, the problem of translation - namely, how genetic information is used to synthesize proteins - was a central topic in molecular biology.

By then, I was making the slow transition from classical biochemistry to molecular biology and becoming increasingly preoccupied with how genes act and how proteins are made.