THEORETICAL-STUDY OF SOME FEATURES OF COM PENSATORY SUBSTITUTIONS IN THE TRANSFER-RNA STEM REGIONS

Some families of isoacceptor tRNAs were studies using VOSTORG software package for phylogenetic analysis. While analysing the evolutionary t rees in was shown that the fixation of double substitutions AU reversi ble GC in spiral double-stranded regions passes two stages with interm ediate station, such as non-canonical base pairs. In all the families studied double substitutions can be explained not only by passages thr ough slightly deleterious GU pairs. Comparative analysis of B2-like re peats shown the absence of compensatory substitutions in the parts whi ch are homologous to RNA stem regions. The data obtained let us assume that compensatory substitutions in the RNA helical regions represent an expressive example of non-directed adaptive molecular coevolution.