This yeast artificial chromosome pYAC3 contains
   telomere  sequences  (TEL),  a  centromere  (CEN4, from chromosome 4),
   necessary for eukaryotic chromosomes. and many gene markers.

   Treatment  with the restriction enzymes SnaB1 and BamH1 breaks it into
   two arms, and target DNA fragments ligated between the arms are cloned
   in yeast host cells.

   YACs  can  carry  up  to  1,000  kb  of  DNA,  and  can also carry out
   posttranslational modifications that eukaryotic proteins require.