"Comma-less codes"

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

Licence: In copyright

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

    13/37
    Go VM. - [pî'i (frtLt, S f,\A-i, C'.xxk , jrs. í]vC-ffitj <à.v*1 i.. E t>r¿j el A¡®*- *ui« 4* ¡fá (iNft Ttt cui - It is assumed In on© of the more popular template theories of protein synthesis that amino acids are ordered on a nucleic acid strand. Since there are some twenty naturally occurring amino acids and only four different nucleotides and since the sequences of amino acids so far determined indicate few if any restrictions on the possible neighbours of a given amino acid, it seems probable that more than one nucleotide is required to determine an amino acid. It is not our purpose here to discuss the plausibility of this assumption, but rather to consider in a formal way, one of the problems which it raises. Since the number of amino acids exceeds sixteen it seems natural to consider first the case in which an amino acid is determined by three bases. The total number of different sequences of three bases is of course sixty four, so that we need to find some reason why the number of amino acids is so mueh smaller. Various explanations hay© already been suggested but here we shall derive the magic number, twenty, by a novel argument. Suppose we have a sequence of nucleotides forming a nucleotide chain and we associate amino acids with successive, .randomly chosen, non-overlapping, consecutive trios of bases as in Pig. 1. .„. GACCUGCÜAGÖACUGCCCAGCÜ .... gly glu arp gly Pig, 1.
    digitised image 1
    digitised image 2
    digitised image 3