DNA (deoxyribonucleic acid). A type of nucleic acid that constitutes the molecular basis of heredity. It is found principally in the nucleus of all cells where it forms part of the chromosome, or in the cytoplasm of cells lacking a nucleus, such as bacteria.NA, n an acronym for deoxyribonucleic acid. A type of nucleic acid that contains genetic instructions for the development of cellular life forms. Capable of replicating itself and of producing another type of nucleic acid known as RNA. n the DNA specific to a bacterial strain.