library_construction_protocol: Cells were stained with live cell double stranded DNA dye, Vybrant DyeCycle Violet Ready Flow (Invitrogen, #R37172) and sorted on the FACS Aria III into 4 fractions: G1, Early, Mid and Late. Single Cell Repli-Seq libraries were constructed using the Chromium 10X Single Cell CNV Solution according to manufacturer's instructions. Equal numbers of Early, Mid and Late cells were pooled prior to use in the Single Cell CNV system to meet the minimum recommended cell recovery number (250 cells). For S-phase cells, we used a ~500 cells/uL stock concentration. For G1 cells, we used a 60 cells/uL stock concentration. Libraries were sequenced on an Illumina NovaSeq 6000 S4 flowcell (200 cycles).