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This work is devoted to a linkage study of the gene controlling esterase D and a lethal factor in domestic pig. Segregation for two alleles EsDB, which originated from populations of miniature swine and pigs of a large white breed, and the effect of these variants on the number of offspring in a litter were compared. The results showed a linkage of locus EsD with a lethal factor. This lethal factor causes the mortality of homozygotes and half of the heterozygotes in a litter, which depends on the litter size. The lethal factor was found to be absent in miniature pigs, and in the large white breed it is predominantly linked with allele EsDB. The effect of the lethal factor on population structure and fecundity is discussed.

Disturbances in segregation of offspring with white and colored coats obtained from crossing pigs heterozygous for gene White (a dominant white coat color) with heterozygotes and homozygotes for recessive alleles are studied. The data obtained, along with available data published earlier, suggest the existence of three alleles of gene Spotted, which is linked to gene White. These are a dominant allele Sp (lack of spots), a recessive lethal allele Splet (lack of spots; prenatal death of the homozygotes) and a recessive allele sp (spots in the pigs heterozygous for gene White).