Drosophila ORC localizes to open chromatin and marks sites of cohesin complex loading

Chromosomal density of ORC is a determinant of replication timing. (A) A histogram of inter-ORC distance throughout the genome. The median distance between ORC binding sites is 11 kb. (B) Time of replication is significantly delayed for sequences between distant ORC binding sites. The relative time of replication for the sequences equidistant from two ORC binding sites was plotted against the distance between the two ORC binding sites. (C) Early-replicating regions of the chromosome have an increased density of ORC binding. ORC binding sites per 100 kb were determined for the earliest and latest quartile of replication timing domains.