This paper aims to present the results on study of tetraploid maize forms containing opaque-2(o2) gene that determines a high lysine content in grain protein, so as to harness the biochemical effect of this mutation at the tetraploid level. Tetraploid o2 forms develop thicker cobs with bigger grains in irregular rows. Grain weight is higher for tetraploids and their componentat parts (embryo, endosperm, pericarp+tip cap) show high variability in their weight and quotas. Analysis of the segregation pattern of o2 mutation of maize tetraploid forms showed random chromosomal segregation in a phenotypic ratio of 35:1, which is confirmed by χ2 test application. With ploidy level increased the amount of grain protein and fat content was reduced. Lysine content in grain protein containing o2 gene increased in proportion to the dose level in triploid and, partly, in the hexaploid endosperm.