In ciliated protozoa, the presence of two morphologically and functionally different types of nuclei. The macronucleus is large, highly polyploid, and it contains many nucleoli. Macronuclear DNA functions analogously to the DNA of somatic cells. The micronucleus functions as the germline and is diploid. It is capable of undergoing meiosis during conjugation (q.v.). The macronucleus develops from a micronucleus. See Classification, Protoctista, Ciliophora; Chronology, 1876, Bütschli, Paramecium aurelia, Stylonychia, Tetrahymena.
Subjects: Genetics and Genomics.