ABSTRACT
The nucleus (see Figure 18.45) is a prominent organelle bounded by a double plasmatype membrane which has pores 40-100 nm in diameter. The outer membrane is granular and continuous with the rough endoplasmic reticulum (ER), and contains ribosomes. Within the inner membrane is a mesh of nuclear plasm interspersed with nuclear ribosomes and chromatin (DNA bound to protein). The pores in the membrane allow the passage of large molecules such as mRNA (see later) on its route from transcription on the DNA into the cytoplasm of the cell. Within the nucleus may be one or more small round bodies, the nucleoli which store RNA. The functions of the nucleus are to:
? contain genetic material of the cell; ? produce ribosomes and RNA; ? play a role in cell division.
