Localization of BrdU-Induced Break Sites in Bovine Chromosomes

SUMMARY

A map of BrdU-induced breaks in chromosomes of cattle has been achieved by using late BrdU incorporation for producing RBA bands in lymphocytes of a female calf affected by chromosome instability. This procedure gave a conspicuous rate of chromosome breaks which were carefully located on a diagrammatic representation of the RBA banded bovine karyotype arranged according to the Reading nomenclature. The sites of BrdU-induced breaks were found to be located at the junctions between R-positive (G-Q negative) and R-negative (G-Q positive) bands and, sometimes, between the centromere and the first subcentromeric band. The distribution of breaks among the chromosomes was found to be proportional to chromosome length. Highly sensitive BardU-break sites have been found in chromosomes 2, 12 and on the short arm of the early replicating X chromosome.