artificial chromosome Synthesized DNA in chromosomal form for use as an expression vector.
aseptic Sterile, free from bacteria, viruses, and contaminants such as foreign DNA.
attenuated Weakened (attenuated) viruses often used as vaccines; they can no longer produce disease but still stimulate a strong immune response similar to the natural virus. Examples include oral polio, measles, mumps, and rubella vaccines.
bacteriophage A virus that infects bacteria, sometimes used as a vector.
base pair Two bases on different strands of nucleic acid that join together. In DNA, cytosine (C) always pairs with guanine (G) and adenine (A) always links to thymine (T). In RNA molecules, adenine joins to uracil (U). .
batch culture Large-scale cell culture in which cell inoculum is cultured to a maximum density in a tank or airlift fermentor, harvested, and processed as a batch.
bioactivity A proteins ability to function correctly after it has been delivered to the active site of the body (in vivo).
bioavailability Measure of the true rate and the total amount of drug that reaches the target tissue after administration.
biologic A therapeutic agent derived f