Nucleus with nucleoles
Graphic of a nucleus with nucleole in blue. The 3D graphic shows the nucleus, that is usually embedded into cytoplasm, from the outside, so that only the nuclear envelope is visible. Nucleoles are found in all eukaryotic cells and thus serve as a distinguishing mark compared to prokaryotes, that don`t have a real nucleus with a double membrane. The genetic information (DNA) is located in the nucleus, in the form of chromosomes. There are also varying numbers of nucleoles. Furthermore the nucleus has pores, through which mRNA segments can leave the nucleus in order to later be translated into an amino acid sequence at the ribosomes in the cytoplasm outside of the nucleus. One quarter of the nucleus is cut out, so that its inside is visible. In the 3D cut, heterochromatin and euchromatin, that contain the genetic information, are depicted in purple. The nucleole is embedded into the chromatin. A human diploid cell usually contains ten nucleoles. Nucleoles are the location of origin of the RNA. During the nuclear division, the nucleoles disappear completely and only reappear in the daughter cells.