Single-sister labeling in the C. elegans germline using the nucleotide analog EdU

Reciprocal exchanges between genetically identical sister chromatids (sister chromatid exchanges or SCEs) have been challenging to study. Here, we describe a protocol that utilizes a pulse/chase of the thymidine analog 5-ethyl-3'-deoxyuridine (EdU) in combination with click chemistry and antibody labeling to selectively label sister chromatids in the C. elegans germline. Labeling has no discernable effects on meiosis, allowing for cytological quantification of SCEs. This protocol can be combined with a variety of imaging approaches, including STED, confocal and super-resolution. For complete details on the use and execution of this protocol, please refer to Almanzar et al. (2021).