Selection of supercontigs from chromosome Unknown (chrUn). The supercontigs from the chrUn are chosen with a minimal size of 10 kb, a minimal overlap with the human alignment net track of 20% and a maximum overlap with the chicken self-alignment table of 20%. A: schematic representation of the filtering and intersection queries in the UCSC table browser. B: screenshot of the UCSC browser, representing a supercontig selected with the above criteria. The overlap with the human alignment net track is about 75% and there is no overlap with another chicken region. The quality scores and repeat element tracks are displayed to guide the choice of PCR primers.