End sequence profiling (ESP) can be used to detect structural variations such as insertions, deletions, and chromosomal rearrangement. Compare to other methods that look at chromosomal abnormalities, ESP is particularly useful to identify copy neutral abnormalities such as inversions and translocations that would not be apparent when looking at copy number variation. From the BAC library, both ends of the inserted fragments are sequenced using a sequencing platform. Detection of variations is then achieved by mapping the sequenced reads onto a reference genome.