Analysis of the frequency of sister chromatid exchange in different regions of chromosomes of the kangaroo rat (Dipodomys ordii).

The frequency of sister chromatid exchanges (SCEs) has been determined for C band and non-C band regions of chromosomes of the kangaroo rat after staining with the fluorescence plus giemsa (FPG) technique. After one complete round of DNA synthesis in the presence of bromodeoxyuridine (BrdU) staining of the C band regions revealed simple or complex asymmetries between chromatids. After two complete rounds of DNA synthesis in the presence of BrdU "harlequin" chromosomes were observed. Analysis of the distribution of SCE in chromosomes at their 1st and 2nd mitosis showed that relatively few exchanges occur within C band regions, although the frequency of SCEs is high at the junction between C band and non-C band chromosome regions.