RESUMEN
The reptile phylogeny is poorly studied, and many existing hypotheses are controversial. In this study, the ITS2 regions of 43 species of lizards, snakes, turtles, and crocodiles were cloned and sequenced in addition to eight ITS2 sequences of amphibians, reptiles, and birds already present in the database. The ITS2 of reptiles, similarly to other vertebrates, contain short conserved (consensus) regions, alternating with variable regions (DI, DII, and DIII), which are potentially capable of forming stable secondary structures. These functionally neutral rDNA regions, separating the consensus regions, are substantially different in size, as well as in the primary and secondary structure. Sequences of the ITS2 variable regions were aligned using the GeneBee Molecular Biology Server software program with subsequent automated construction of prescribed trees. The trees for all three variable regions were highly similar, enabling certain conclusions on the evolutionary history of reptiles.