Cell nuclei were purified by a FACSAria II SORP flow cytometer and sorter (BD Biosciences, San Jose, CA) equipped with UV laser for DAPI excitation. Populations of G1 nuclei were sorted in batches of 700 000 into 1.5‐mL polystyrene tubes containing 660 μL IB buffer. In total, four batches of nuclei were sorted and each batch was used for preparation of one 20‐μL agarose miniplug. DNA embedded in miniplugs was purified by proteinase K (Roche, Basel, Switzerland) treatment according to Šimková et al. (2003). The miniplugs were washed four times in wash buffer (10 mm Tris, 50 mm EDTA, pH 8.0) and five times in TE buffer (10 mm Tris, 1 mm EDTA, pH 8.0) and then melted for 5 min at 70 °C and solubilized with GELase (Epicentre, Madison, WI) for 45 min. A drop dialysis against TE buffer (Merck Millipore, Billerica, MA) was performed for 90 min to purify DNA from any residues and subsequently quantified using a Quant‐iTTM PicoGreen® dsDNA assay (Thermo Fisher Scientific, Waltham, MA).