Polymorphism of the genes associated with the formation of productive traits of animals is studied in order to increase the breeding efficiency. The article presents the results of DNA genotyping and live weight indices of replacements of the Dagestan mountain sheep in the age dynamics. The animals carrying the desirable breeding-relevant allele GHB and having heterozygous genotype GHAB surpassed their peers carrying homozygous genotype GHAA in live weight by 2.9 % at the age of 2 months, by 3.5 % at the age of 4 months, and by 5.4 % at the age of 8 months. The index of live weight of the animals carrying the desirable breeding-relevant allele GDF9A with heterozygous genotype GDF9AG and homozygous genotype GDF9AA was several times higher than the one of their peers carrying homozygous genotype GDF9GG; they differed by 5.0 and 10.1% at the age of 2 months, by 2.0 and 5.7% at the age of 4 months, and by 2.4 and 6.1% at the age of 8 months, respectively. The study revealed complex genotypes with the allelic profile represented by one (GHAAGDF9AG), two (GHAAGDF9AA), and three (GHABGDF9AA) selection-relevant marker alleles. It was noted that greater values of live weight were in the animals carrying complex genotypes GHAAGDF9AA, GHAAGDF9AG and GHABGDF9AA, amounting to 14.8, 14.5, 15.3 kg at the age of 2 months, 26.4, 26.2 and 26.9 kg at the age of 4 months, and 33.6, 33.8 and 34.9 kg at the age of 8 months, respectively, against the peers carrying complex genotype GHAAGDF9GG, amounting to 14.3, 25.8 and 32.8 kg, respectively.