Overlapping BACs in library with depth d = 12-fold. A typical BAC (shown in black) will tend to have 12 BACs overlapping its right end and 12 BACs overlapping its left end. Each overlapping clone can be identified because one of its end sequences (shown by arrowheads) is contained within the sequence of the target BAC. The precise position of each overlapping clone is inferred by the location and orientation of the end sequence within the sequence of the target BAC.