The specific character of distribution of mononucleotide tracts and mixed W or S tracts in human Y and 22 chromosomes was analysed by comparative genomic approaches. It was found that in regulatory regions of Y chromosome anomalously high density of S (G/C)-tracts consisting of relatively short sequences (up to 6 base pairs) was observed. In primary structure of coding regions (exons) of 22 chromosome only a small redundancy of S- tracts was discovered. Previously in our papers we pointed to the non-trivial, increased ability of G/C pairs to a spontaneous change in the geometry of its complementary H-binding (because of the different dimensions of the hidden structural polymorphism of Watson-Crick G/C and A/T base pairs) in comparison with A/T pairs. In this case, revealed high density of S(G/C)-tracts in intergenic regions of Y chromosome indicated to possibility of increasing in the number of events of spontaneous complementarity lesions in this areas in comparison with similar events in the autosomic 22 chromosome. That is, in this way an abnormally high frequency of spontaneous point mutations in the Y chromosome compared with the frequency of similar mutations in other human chromosomes can be initiated. This is observed experimentally.
DNA, chromosome structure, redundancy of S-tracts, structural polymorphism of Watson-Crick base pairs, frequency of spontaneous mutations
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