In the present study, for the first time we investigated the genetic diversity among horse breeds from Bosnia and Herzegovina: potential Bosnian and Herzegovinian mountain horse, Arabian horse, Thoroughbred horse and crossbreeds, with special emphasis on the gene pool of potential Bosnian and Herzegovinian mountain horse. In total, 138 animals were genotyped for 17 microsatellite loci. Compared to the other breeds, potential Bosnian and Herzegovinian mountain horse showed quite a high genetic variability. The mean number of alleles was 14.1765. The average observed heterozygosity was 0.6589 and the expected heterozygosity was 0.8451. The mean value of polymorphic information content was 0.8286. The results of AMOVA test showed 8,44% of genetic variation among populations. The highest genetic variation within population was showed by potential Bosnian and Herzegovinian mountain horse (27.13). The same breed showed the highest individual variation (17.35). Overall FST value showed high level of the genetic differentiation among breeds (8.87 %), and the pairwise FST values were all significant. Highest inter-group genetic differentiation was observed among Arabian horse and Thoroughbred horse (groups of pure breeds) and potential Bosnian and Herzegovinian mountain horse. The results show that the potential Bosnian and Herzegovinian mountain horse has a high in-breed variability, more than could be expected. In the gene pool of potential Bosnian and Herzegovinian mountain horse, a part of the gene pool of other breeds is present. Also, these results show that there are very good preconditions for the revitalization of the gene pool of potential Bosnian and Herzegovinian mountain horse. Keywords: Horse, genetic diversity, microsatellites

Ionising radiation is known to cause chromosomal instability, which is observed as increased frequency of chromosomal aberration and micronuclei. These are listed as reliable criteria in biological dosimetry. Numerous experiments conducted on both animal and plant models demonstrated that increase in radiation dosage is followed by increased mutation frequency, and that mutations occur even at the lowest exposure. We used horse blood in vitro irradiated by low doses of ionizing radiation. Cultivation of peripheral blood lymphocytes and micronucleus test were used as biomarkers of genetic damage. The observed aberrations were recorded and classified in accordance with the International System of Cytogenetic Nomenclature. Micronuclei were identified on the basis of criteria proposed by Fenech et al . (8). Analysis of chromosomal aberration showed increased frequency of aberrations in blood cultures exposed to 0,1 Gy and 0,2 Gy compared to the controls. Microscopic analysis of chromosomal damage in in vitro micronucleus test revealed that the applied radiation dose induced micronuclei while no binucleated cells with micronuclei were found in lymphocytes that were not irradiated. In this paper we analysed the influence of low dose ionising radiation on frequency of chromosomal aberration and micronuclei in horse lymphocytes following in vitro exposure to X-rays (0,1 Gy and 0,2 Gy). Key words : chromosomal aberrations, micronuclei, ionising radiation, horse lymphocytes