A  bacterial  artificial chromosome (BAC) ia a
   vector with a large cloning capacity (up to 300 kb).

   A  BAC is constructed from a fertility plasmid (F factor) that enables
   conjugation.

   A  chloramphenicol  resistance gene serves to screen for recombinants,
   while  a  polylinker  contains  several restriction enzyme recognition
   sites for inserting foreign DNA.

   Promoter regions at T7 and Sp6 allow expression of inserted genes.