mRNA: Syntax Organization

The purpose of the article is to analyze the features of the primary mRNA structures, considering them in the context of linguistics as characteristics of their syntax, and to find out what causes the limitations in gene coding. For computer analysis, databases of primary mRNA structures of various genes of various organisms available on the Internet were used to determine the distribution of complementarity indices (CI) and codon dimension indices in mRNA tricodons, the frequency of occurrence of codons in mRNA by their index values and their translational codes. A universal pattern of the closest proximity of codons in tricodons has been identified, repeating the restrictions of the proximity of tricodons: the first and third codons flanking the second codon have predominantly identical or similar index values, and the first and third codons exhibit stricter restrictions on index values. The connectivity between the first and third codons in tricodons is also manifested in the existence of forbidden and rare combinations of them. The frequency of occurrence of codons in dicodons that lack the anticodon tRNA gene varies greatly. The repertoire of tricodons in mRNA is very limited, which significantly narrows the possibilities of gene recoding. In mRNA translational codes, the connectivity of dominant codons in terms of nucleotide identity (or their CI) in their third position has been revealed. The list of characteristics of the syntax of primary mRNA structures is given. The similarity of the limitations on the CI values of sequentially read tricodons and between codons in tricodons leads to the recognition of the existence in genes (mRNAs) of a continuum of linear connectivity of codons in terms of their CI values. The limitations in gene coding are due to the ban on the use of a significant number of tricodons and the predominant use of dominant codons.