Aim. Out of 8 thousand species of mammals, dog is the first domesticated animal. Archaeologists studying the process of human evolution and producing excavations of ancient sites, found the bones of animals, which man ate and also bone remains of animals that lived near the sites. Wolf was the first domesticated animal of primitive tribes. This process began in the Mesolithic era 12–15 thousand years ago. Due to domestication of wolf population many indigenous, transitional and other breeds of dogs appeared. Methods. Using morphological, biochemical and genetic methods of research scientists were able to determine genome and karyotype of wild European wolf and domestic dog. Results. Domestication is a process of historical transformation of wild animals into domesticated ones. Nowadays taking into account genetics research, cytology and special experiments, researchers-cynologists came to the conclusion that only wolf is a direct ancestor of modern dogs. This is confirmed by the fact that wolf and dog have 78 chromosomes and after mating we get fertile litter. The domestication of dogs is a complicated process. While domestication of dogs to the new conditions occurred in captivity, genetic mechanisms well-known to us played an important role – mutation, recombination, hidden reserve of heredity, the direct effect of selection. Conclusions.It was proved by our research that the process of breeding in dogs which appeared as a result of domestication and microevolution of animals was accompanied by specialization and genetic differentiation of dog breeds. Кeywords: wolf, dog, domestication, karyotype, breed.