Sister chromatid exchanges (SCE) in the cattle popolation Agerolese

The sister chromatid exchange (SCE) test has been used to check genome (DNA) stability of humans (Chaganti et al., 1974) and the main livestock species (Di Meo et al., 2000; Iannuzzi et al., 1990; Lopez and Arruga, 1992), as well as to discover DNA damage caused by a range of natural and artificially synthesised chemical compounds. The SCE test can be performed during DNA replication, after two cell-cycle–replications in the presence of the thymidine analogue 5-bromodeoxyuridine (BrdU). While the sister chromatid with a native polynucleotidic chain (containing thymidine) is stained, the other sister chromatid, with BrdU in both polynucleotidic chains, is not stained. This allows easy visualization of the presence of SCEs. High number of SCEs is evidence for high genome instability and occurrence of possible mutations. The SCE test has also been used to determine the frequency of exchange on the active and inactive X chromosome in bovids (Iannuzzi et al., 1990) to compare genome stability of three different cattle breeds reared under similar conditions (significant differences in SCE mean values were found between Friesians— with lower numbers of SCE—and the Podolians) (Iannuzzi et al., 1991); and to compare the mean SCE values of animals with a normal karyotype and those (with significant higher SCE/cell mean values) carrying rob (1;29) (Rangel-Figueiredo et al., 1995). The aim of this work was to apply the SCE test on the Agerolese cattle population so as to check the genome stability of this endangered breed.