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.