amino acid An organic molecule containing three functional groups—an amino group, a carboxyl group, and a distinct side chain—attached to a central carbon. Amino acids are the building blocks of proteins.
angiogenesis The formation of new blood vessels, for example, to supply blood to a new tumor.
antibody A protein derived from B lymphocytes that attaches to surface molecules on bacteria, viruses, or cancer cells and facilitates their destruction by the immune system.
antigen Any molecule or substance that the immune system recognizes as foreign.
antisense therapy When the genetic sequence of a target gene involved in disease is known, scientists can construct a complementary RNA sequence (antisense RNA) that binds ...