defined: Extremely large segments of DNA from another species spliced into DNA of yeast. YACs are used to clone up to one million bases of foreign DNA into a host cell, where the DNA is propagated along with the yeast cell's other chromosomes.
explained: Dr. Eric Green, of the National Human Genome Research Institute's Genome Technology Branch, defines yeast artificial chromosome (YAC).

Related terms: base pair, chromosome, cloning, deoxyribonucleic acid (DNA), Human Genome Project.