Animal Biotechnology

YEAST ARTIFICIAL CHROMOSOME (YAC)

• YACs are artificial chromosomes that replicate in yeast cells.
• They consist of
  • Telomeres (TEL), which are ends of chromosomes involved in the replication and stability of linear DNA.
  • Origin of replication sequences necessary for the replication in yeast cells.
  • A yeast centromere (CEN), which is a specialized chromosomal region where spindle fibers attach during mitosis.
  • Autonomous replicating sequence (ARS).
  • A selectable marker for identification in yeast cells.
  • Ampicillin resistance gene for selective amplification.
  • Recognition sites for restriction enzymes.
• The yeast artificial chromosome (YAC) vector is capable of carrying a large DNA fragment (up to 2 Mb), but its transformation efficiency is very low.
• Steps in YAC cloning
  • The target DNA is partially digested by EcoRI and the YAC vector is cleaved by EcoRI and BamHI.
  • Ligate the cleaved vector segments with a digested DNA fragment to form an artificial chromosome.
  • Transform yeast cells to make a large number of copies.