Nucleus serves as a centre for controlling all the activities of the cell
- Robert Brown in 1831 was the first individual to observe nucleus.
- The discovery of nucleus was a revolutionary step which disregarded the concept of cell being an empty compartment bound by thick walls
- In animal cell, the nucleus occupies a central position.
- In plant cell, the nucleus is pushed towards the periphery by the central vacuole.
NUCLEI PER CELL:
- Generally, cells contain a single nucleus and are termed as mono-nucleate cells.
- Cells containing two or more nuclei are termed as multi-nucleate cells.
- Nucleus is only visible under the microscope when cell is in non-dividing stage. It contains chromatin material and soluble sap called nucleoplasm.
- In dividing cell, the nucleus disappears and the chromatin material in it is replaced by chromosomes.