The monograph by A. G. Skavronskaya "Mutations in bacteria" contains the main experimental data obtained in studies with bacterial cells, which served as the basis for the development of a new branch of genetic science - molecular genetics. The main provisions of the modern chromosomal theory of heredity were discussed, in particular, issues related to the nature of genetic determinants, their fine structure, the mechanism of genetic coding, etc. In the light of chromosomal theory, data regarding mutational variability are presented. Particular attention is paid to the analysis of work on the mutagenic effect of analogs of natural DNA bases and radiation. The data obtained in the study of bacterial mutagenesis are also summarized, which made it possible to clarify some mechanisms for the implementation of genetic information embedded in structural genes and the regulation of protein synthesis.