[Nucleases. Biological role].

In the first part of the review (R. I. Tatarskaya, 1976, Mol. Biol. 10, 235--259) the role of nucleases in the transcription, DNA replication, recombination and reparation was briefly described and discussed. The second part comprises some data on the role of nucleases in tRNA, rRNA, mRNA and DNA processing and mRNA degradation. Brief chapters "Restriction" and "Nucleases and viruses" are included as well.