"A membrane-bounded organelle of eukaryotic cells in which chromosomes are housed and replicated. In most cells, the nucleus contains all of the cell's chromosomes except the organellar chromosomes, and is the site of RNA synthesis and processing. In some species, or in specialized cell types, RNA metabolism or DNA replication may be absent [goid 5634] [evidence IEA]; The sex chromosome present in both sexes of species in which the male is the heterogametic sex. Two copies of the X chromosome are present in each somatic cell of females and one copy is present in males [goid 805] [evidence IEA]; The sex chromosome present in males of species in which the male is the heterogametic sex; generally, the sex chromosome that pairs with the X chromosome in the heterogametic sex. The Y chromosome is absent from the cells of females and present in one copy in the somatic cells of males [goid 806] [evidence IEA]; A structure found in a male mammalian spermatocyte containing an unpaired X chromosome that has become densely heterochromatic, silenced and localized at the nuclear periphery [goid 1741] [evidence IEA]; A membrane-bounded organelle of eukaryotic cells in which chromosomes are housed and replicated. In most cells, the nucleus contains all of the cell's chromosomes except the organellar chromosomes, and is the site of RNA synthesis and processing. In some species, or in specialized cell types, RNA metabolism or DNA replication may be absent [goid 5634] [evidence IEA]; All of the contents of a cell excluding the plasma membrane and nucleus, but including other subcellular structures [goid 5737] [evidence IEA]; Any complex that mediates dynamic changes in eukaryotic chromatin [goid 16585] [evidence IEA]; Any chromosome other than a sex chromosome [goid 30849] [evidence IEA]; A ribonucleoprotein complex found in the cytoplasm of male germ cells, composed of exceedingly thin filaments that are consolidated into a compact mass or into dense strands of varying thickness that branch to form an irregular network. Contains mRNAs, miRNAs, and protein components involved in miRNA processing (such as Argonaute proteins and the endonuclease Dicer) and in RNA decay (such as the decapping enzyme DCP1a and GW182) [goid 33391] [evidence IEA]"