Hierarchical structure of donor splice site sequence multitude.

An analysis of donor splice site sequence (dsss) multitude was carried out. A special method was developed to study the multitude properties. The multitude of dsss was arranged as a hierarchical tree where the "root" consists of a small group of "ancestors", VAGgtVAG (gt stands in the beginning of intron, V=C,A,G). Every ancestor has its own clan of "descendants" which represent point mutants of it. The latter are split into "progenies". The first progeny looks like point mutants of the ancestors, the second as one-point mutants of sequences of the first progeny, and so forth. This picture looks like a hierarchical phylogenetic tree. The most striking property of the multitude is the successive monotonic decrease in occurrences of the sequences from one progeny to another. It is shown that such results may be modeled by a virtual mutational process.