Also found in: Medical.
nucleocytoplasmic ratio[¦nü·klē·ō‚sīd·ə′plaz·mik ′rā·shō]
(also nucleoplasmic ratio), in biology, the ratio of nuclear to cytoplasmic volume. The ratio was introduced in 1908 by the German scientist R. Hertwig, who believed that regular decrease in the nucleocytoplasmic ratio was the immediate cause of the initiation of cell division. Hertwig’s hypothesis has not been confirmed. The volume of the nucleus is usually directly proportional to the volume of the cytoplasm, including the case of polyploidy of the nucleus. However, many exceptions to this proportionality are known, for example, in the development of egg cells or in changes of the functional activity of a cell. Cells of different tissues have different nucleocyto-plasmic ratios; therefore, the ratios are used to characterize cell types.