[Mutagenic process in bacteriophage T4B after long-term exposure to a mutagen].

Bacteriophage T4B was continuously passed on solid media in the presence of 5-bromodeoxyuridine in two simultaneous experiments. The subsitutions of amino acids were registered, and in one of the experiments biological changes were revealed in non-optimal conditions. Calculations has shown that the number of amino acid substitutions observed corresponds to at least 140--200 fixed mutations. The possibility of the mutation fixation via selection is discussed and their relative neutrality is suggested.