The aim of the research was to quantify the location and movement of the DNA replication factors ORC and MCM in the context of chromatin at the single-molecule level.This was achieved using a combination of optical tweezers and confocal fluorescence microscopy. The position along DNA molecules held in an optical trap of fluorescently labelled H2A, ORC and MCM was tracked over time, and position and motion parameters (e.g. localization and diffusion constants) were studied under different biochemical conditions.