EN
The exchanges between sister chromatids were detected with the fluorescence plus Giemsa technique, in which the thymine analogue, bromodeoxyuridine, was used for DNA labelling. This method was used to examine the influence of bovine leukaemia virus on chromosomal disorders in bovine blood lymphocytes. In metaphasal chromosomes of BLV infected lymphocytes, numerous sister chromatid exchanges (SCEs) were found. In chromosomal spreads of lymphocytes of BLV infected cows there were 6.5-13.0 SCEs per metaphase. In the control animals, only a small number of spontaneous SCEs (0-2.0) were found (P<0.01). The obtained results indicated that BLV may cause chromosomal disorders in lymphocytes of leukaemic cattle.