Methods for detecting genomic rearrangements are provided. In one embodiment, methods are provided for the use of paired end tags from restriction fragments to detect genomic rearrangements. Sequences from the ends of the fragments are brought together to form ditags and the ditags are detected. Combinations of ditags are detected by an on-chip sequencing strategy that is described herein, using inosine for de novo sequencing of short segments of DNA. In another aspect, translocations are identified by using target specific capture and analysis of the captured products on a tiling array.