Unlike most cell-based thymidine analogassay kits that can only measure qualitative differences in incorporation, the CytoSelect™ EdU Competitive ELISA Kit quantifies EdU incorporated into cellular DNA. The unknown DNA samples or standards are first added to a microplate preadsorbed with a EdU conjugate. After a brief incubation an anti-EdU monoclonal antibody is added, followed by an HRP-conjugated secondary antibody. The EdU in solution and the EdU coated on the plate compete for binding of the antibody. If no EdU is in solution, all of the antibody will bind to the plate resulting in a high signal. High levels of EdU in solution will bind the antibody and be washed away, resulting in a low signal.