[Divergence of repetitive DNA sequences in Echinodermata. I. Comparison of sequences with a high degree of intragenomic divergence].

The molecular DNA-DNA hybridization method was used for comparison of repetitive sequences with a high degree of intragenomic divergence in seven species of echinodermata, representatives of three classes of this type, and also for a representative of the type Annelida. The value of intragenomic divergence was estimated with respect to a thermolabile fraction of repetitive [3H]DNA of Strongylocentrotus intermedius isolated by thermoelution at 70 degrees after reassociation up to C0t=140. The data obtained indicate a significant conservatism of the given fraction: its homologues are present in DNA of all the species studied. Hybridization of the thermolabile fraction of [3H]DNA S. intermedius at C0t=10 and 1000 allowed one to estimate the divergence of sequences in DNA of all the species studied. Hybridization of the thermolabile fraction of [3H]DNA highly repetitive sequences of the given DNA fraction is more appreciable than that of moderately repetitive ones. Intragenomic divergence of moderately repetitive thermolabile sequences is higher than that of highly repetitive sequences both in phylogenetically close and distant species of sea urchins.