Large segments of DNA, 100,000 to 200,000 bases, from another species cloned into bacteria. Once the foreign DNA has been cloned into the host bacteria, many copies of it can be made.

Dr. Eric Green, of the National Human Genome Research Institute's Genome Technology Branch, defines BAC (bacterial artificial chromosome).
related terms: base pair, chromosome, cloning, deoxyribonucleic acid (DNA), genome, yeast artificial chromosome (YAC) .