The nucleus is an organelle typically occupying about a tenth of the eukaryotic cell volume. It has a central role in gene expression, heredity and cell division by virtue of the presence of DNA. Indeed, the nucleus theoretically acts as a haven for precise interpretation of the genetic code away from the myriad of cytoplasmic functions.
There are a variety of proteins present which aid function e.g.:
- DNA-binding proteins - histones
- DNA polymerases
- RNA polymerases
- RNA transcript processing enzymes
- gene regulatory proteins
- ribonucleoprotein complexes containing messenger RNA
DNA may be stored in a variety of ways within the nucleus e.g. within chromosomes, chromatids, chromatin, nucleosomes, Barr body or nucleolus. The nucleolus has a special function as the origin of ribosomal RNA. All nuclear components are suspended in amorphous nucleoplasm - karyolymph - and enveloped by a specialised nuclear membrane.
A few cells have dispensed with the nucleus at the expense of function e.g. haemoglobin storage in the mature erythrocyte.
Last reviewed 01/2018