It is assumed that changes in the number of copies that belong to the basic mechanisms that control the expression of genes are important for malignization. Therefore, the characterization of these genes and the precise assessment of the number of copies are important for understanding the molecular basis of tumor emergence and progression in the human organism, as well as for the identification of predictive markers of malignization. In the present study, the relative number of copies of 19 loci (BAX, GSTP1, CASP3, CASP8, HIF1A, OCT4, C-MYC, SOX2, BCL2, CASP8/FADD, NANOG, P53, CASP9, IL-10, NFKB1, HV2, and ACTB) in cancerous and conventionally healthy tissues from 25 residents of southern Russia with a histologically confirmed diagnosis of adenocarcinoma (stages G1-G2 and G3) or signet cell gastric cancer were determined by quantitative real-time PCR. Changes in the number of copies of the gene were shown to be specific to particular histological types of cancer, as well as to depend on the stage of tumor cell differentiation. The data suggest that the number of copies of changes in the BAX, CASP3, CASP8, OCT4, C-MYC, SOX2, BCL2, NANOG, CASP9, NFKB1, HV2, ACTB, MKI67, IL-10, GSTP1, and P53 genes play an important role in the malignization of gastric tissue.