Identification of replication origins by deep sequencing of hydroxyurea-arrested cells. (a) The replication profile of a region of S. pombe dataset Sp1 containing three validated origins and several AT islands. The red curve shows the normalized replication fraction in HU-arrested cells. The blue dots show identified replication peaks. On the x-axis, black represents genes, orange represents AT-rich intergenes  and green represents validated origins (collated in ). (b) The difference between the G2 datasets form Sp1 and Sp2, demonstrating the magnitude of the noise in the datasets. (c) The replication profile of a region of S. octosporus dataset So1, as in (a). (d) The replication profile of a region of S. japonicus dataset Sj2 containing two cloned ARSs , as in (a). ORF, open reading frame.