Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Distribution and sources of variability of sister-chromatid exchange frequencies in cattle | 3 Genet Sei Evol 1994 26 3-14 Elsevier INRA Original article Distribution and sources of variability of sister-chromatid exchange frequencies in cattle J Catalan1 c Moreno2 MV Arruga1 1 Laboratory of Cytogenetics 2 Quantitative Genetics Unit Veterinary Faculty Miguel Servet 177 50013-Zaragoza Spain Received 25 August 1993 accepted 12 October 1993 Summary The spontaneous incidence of sister-chromatid exchange SCE was investigated in a group of cattle composed of 24 animals of both sexes belonging to different breeds ages and farms. The work was carried out following a randomized block design. The mean value of SCEs cell was using 5 pg ml of bromodeoxyuridine BrdU . The distribution of SCE frequency fits the Poisson model fairly well although the negative binomial model also gave a good representation of exchange distribution. Among the analyzed sources of variability group animal and treatment of BrdU factors showed significant effects. A newly introduced BrdU treatment demonstrated that the number of BrdU molecules available per cell has little influence on SCE rates in relation to its molarity. sister-chromatid exchange distribution frequency bromodeoxyuridine cattle Resume Distribution et sources de variation des frequences d echange entre chroma-tides-soeurs chez les bovins. L incidence spontanée des échanges entre chromatides-soeurs ECS a été étudiée chez 24 bovins de differents sexes races ages et exploitations. L étude a été menée suivant un dispositif en blocs randomises. Le nombre moyen ECS cellule a été de 5 77 0 082 en utilisant 5 ựg ml de bromodéoxyuridine BrdU . La distribution de frequence des ECS suit principalement un modèle de Poisson bien qu un modèle binomial negatif donne aussi une bonne representation de la distribution. Parmi les sources de variation analysées les facteurs groupe animal et traitement du BrdU ont montré des effets significatifs. Un traitement de BrdU introduit récemment a montré que le nombre de molecules de BrdU .
