The nucleus stores the genetic material of the cell as chromatin (DNA + histone proteins)

• The chromatin is contained within a gel-like solution called the nucleoplasm (as opposed to the external cytoplasm)

• By housing the cell’s genetic material, the nucleus acts as a control centre (regulates the expression of genetic instructions)

The nucleus is surrounded by a double membrane called the nuclear envelope, which is embedded with pores

• The nuclear envelope is a double membrane structure because it is part of the endomembrane system (it is connected to the ER network)
  

• This means that proteins synthesised by the ER can access the nucleus without requiring vesicular transportation
  

• The nuclear envelope also functions as a barrier to separate the processes of transcription and translation (prokaryotes lack this separation)
  

• The presence of pores allows the cell to control the rate at which these interlinked processes can occur (coordinates gene expression)
  

A double membrane is also beneficial to the process of mitosis and meiosis (nuclear division in eukaryotic cells)

• During these processes, the nuclear envelope must be disassembled to allow the chromosomes to be sorted and separated

• Because it is a double membrane structure, the envelope can break down into vesicles – these can be reconstituted to reform the nuclear envelope at the end of the division process

Structure of the Nucleus