FEATURES OF CHROMOSOMAL SET OF SHEEP OF ROMANOV BREED
Animal Breeding and Genetics
During long time a great interest was revealed to the Romanov breed by many sheep farmers of the world. To preserve and develop the breed, it is necessary to use modern approaches to assess its inbred breed diversity. One of most perspective for population-genetic researches is cytogenetic that allows to investigate the integrity of the chromosomal set and prevent the spread of unwanted genetic abnormalities in the population. The spontaneous chromosomal to aberration have a selective value in
... selective value in a breed formative process, that are fixed in generations. A level of chromosomal polymorphism is additional description of tribal value of animals, that can be taken into account at the selection of animals of wanted type. An analysis of chromosomal polymorphism of sheep is basis for forming of new knowledge about the dynamics of genetic structure in the populations of animals. The cytogenetics of animals collected considerable knowledge about influence of karyotype on the processes of individual development. With the help of cytogenetic studies, changes in chromosomes that are transmitted to offspring, and correspondingly affect the signs of an animal's organism, are detected. The object of the study was the number of sheep of the Romanov breed (n = 10), which are breeding in the breeding farm "Bach and family" (Kyiv region). The material for chromosomal preparations was the blood of sheep aged 1 to 3 years old that was taken from the jugular vein. The cytogenetic study was carried out at the Genetics Laboratory of the Institute of Animal Breeding and Genetics named after M.V.Zubeta (Chubinskoye village) using special techniques and related equipment. To obtain the preparations of chromosomes, samples of the culture of leukocytes of peripheral blood of animals were used. For analysis and photographing, those metaphase plates were selected, in which the chromosomes were separate from each other. On one drug (glass), from one to ten metaphase plates were examined, and to analyze the karyotype, 50 and more metaphase plates were analyzed. Obtained experimental data was processed by the method of variation statistics using the computer programs EXCEL. The results of the cytogenetic analysis of the sheep of the Romanov breed showed that they all have a chromosomal set typical of the domestic breed of sheep. The chromosomal set of investigated sheep is represented by 54 chromosomes, of which 26 pairs of autosomes and one pair of sex chromosomes (XX or XY). The results of the metaphysical analysis allowed to fix a certain part of stable aberrations. Among 457 metaphase plates 81 aberrant cells (17.7%) were identified, of which aneuploid cells – 6.25%, polyploidy – 0.75%, cells with chromosomal ruptures – 0.25%, chromosomal pair fragments frequency – 0.37%, and the frequency of cells with asynchronous divergence of the centromeric regions of the chromosomes (ARTSRH) was 2.5%. Since the frequency of aberrant cells (n = 240) in a small population is 17.7%, this indicates that the detected violations in the chromosomal set of sheep are not accidental in nature and have an heritable basis. Thus, the results of the cytogenetic study of the sheep of the Romanov breed obtained from us show that their karyotypes have a characteristic chromosome set and structure for this species of animals. At the same time, in the studied animals, there is an individual chromosomal variability, which in turn may be associated with their productive or reproductive qualities. This argument is the basis for continuing our research on the chromosomal polymorphism of sheep of Romanov and other breeds.