Universite de Montpellier 1 article published in JoVE Biology Determination of S-Phase Duration Using 5-Ethynyl-2'-deoxyuridine Incorporation in Saccharomyces cerevisiae Juan de Dios Barba Tena1, Etienne Schwob1, Nicolas Talarek1 1Institut de Génétique Moléculaire de Montpellier, Université de Montpellier, CNRS We describe two complementary protocols to accurately determine S-phase duration in S. cerevisiae using EdU, a thymidine analog, which is incorporated in vivo and detected using Click chemistry by microscopy and flow cytometry. It allows for the easy characterization of the duration of DNA replication and overlooked replication defects in mutants.