The Sister-Chromatid Exchange Assay in Human Cells

Abstract

The semiconservative nature of DNA replication allows the differential labeling of sister chromatids that isthe fundamental requirement to perform the sister-chromatid exchange (SCE) assay. SCE assay is apowerful technique to visually detect the physical exchange of DNA between sister chromatids. SCEscould result as a consequence of DNA damage repair by homologous recombination (HR) during DNAreplication. Here, we provide the detailed protocol to perform the SCE assay in cultured human cells. Cellsare exposed to the thymidine analog 5-bromo-20-deoxyuridine (BrdU) during two cell cycles, resulting inthe two sister chromatids having differential incorporation of the analog. After metaphase spreads prepara-tion and further processing, SCEs are nicely visualized under the microscope.