"Comma-less codes"

Date:
1956
Reference:
PP/CRI/H/2/3
Catalogue details

Licence: In copyright

Credit: "Comma-less codes". Source: Wellcome Collection.

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    Finally we assume that nucleotide sequences corresponding to all possible amino acid sequences are allowed and ask what is the maximum possible number of different amino acids. The nature of this rather abstract problem will be made clear by the following detailed discussion. (1) Sequences of three identical nucleotides make non- senee. Proof Suppose AAA were associated with an amino acid a. Then since the amino acid sequence aa is possible so also is the base sequence AAAAAA. However this sequence can be misinterpreted by associating a with the second to fourth, or third to fifth nucleotide. (2) Not more than twelve sequences of 3 nucleotides, two being identical (for example, AAB) can make sense. Proof No two such sequences with the same composition (e.g. AAB and ABA) can make sense, for if AAB make sense and is associated with a, then the sequence aa or AABAAB, is possible. This can be misinterpreted unless ABA and BAA make nonsense. (3) Not more than eight sequences of three différant nucleotides can make sense. Proof Suppose ABC makes sense and corresponds to a. Then BGA and CAB are forbidden. However one of BAC, CBA, ACB is still allowed. In other words not more than two sequences of identical composition are possible, one being an even and the other an odd permutation of the three constituents.
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