Yeast artifical chromosomes

Yeast Artificial Chromosomes (YACs) is a vector used to clone larger pieces of DNA (100-3000kb). The YAC is digested with restrictions enzymes EcoR1 and BamH1 to create two linear pieces of DNA with sticky ends that eventually house a large piece of DNA from the species being sequenced. The YAC is then able to replicate many times with the foreign DNA to make a library of segments of a genome.
YACs can be scanned for desired sequences to isolate a gene location.
Reference:
http://www.accessexcellence.org/RC/VL/GG/YAC.php