title: Sister chromatid exchange in chromosomes of cattle (Bos taurus).
abstract: Lymhocytes from clinically healthy Holstein animals (8 males and 23 females) were cultured in media containing 5-bromodeoxyuridine (10 microgram/ml) for two cycles of deoxyribonucleic acid replication (48 h). The exchange of sister chromatids per cell varied from 1 to 16 with a mean of 5.4 and a standard deviation of 2.1 in 603 differentially stained metaphase chromosome spreads. The major fraction of exchanges in the X chromosome were located in the region of the subcentromeric G negative bands q1 and q2. When the cells were pulse labeled with tritium labeled thymidine (1 muCi/ml) for the last 6 h of the cell cycle, the rate of exchange was higher in the late replicating X chromosome (facultative heterochromatin) in comparison to its homologue (active X). This study characterizes the yield of sister chromatid exchange in lymphocytes exposed to a given amount of 5-bromodeoxyuridine in a population of normal individuals so that it may be used as a standard for 1) a diagnostic tool in pathological conditions and 2) as an assay of chromosome stability in relation to environmental hazards.
mesh_terms: D000818:Animals; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002417:Cattle / Q000235:genetics*; D002503:Centromere / Q000502:physiology; D002842:Chromatids / Q000502:physiology*; D002871:Chromosome Banding; D002875:Chromosomes / Q000502:physiology*; D004261:DNA Replication; D005260:Female; D008214:Lymphocytes / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008677:Metaphase; D013936:Thymidine / Q000378:metabolism; D014960:X Chromosome / Q000502:physiology; D014998:Y Chromosome / Q000502:physiology
chemical_list: D001973:Bromodeoxyuridine; D013936:Thymidine