The map contigs track shows the locations of contigs of clones on the physical map. In assembly versions before the August 6 freeze this track was based on the Washington University accession map, which in turn was based on a fingerprint contig (FPC) map described in 'A physical map of the human genome' in Nature volume 409 pages 934-941. Starting with the August 6 freeze this track is based on tiling path (TPF) maps curated by the sequencing centers responsible for each chromosome. Imre Vastrik at the European Bioinformatics Institute merges the TPF maps with the FPC map, favoring the TPF map where there are conflicts. This step increases the clone coverage substantially over that in the TPF maps. This merged map is then used as the basis for the UCSC assemblies. The clone contigs in this merged map are shown in this track.