Cell nucleus structure, illustration. The nucleus contains the cell's genetic information in the form of DNA (deoxyribonucleic acid). The DNA is complexed with proteins and stored as chromatin. At centre is the nucleolus, which is responsible for producing components of ribosomes, the cell's protein-manufacturing organelles. The nucleus is surrounded by a membrane that has pores to allow the transport of molecules into and out of the nucleus. Surrounding the nucleus is rough endoplasmic reticulum (RER), the site of protein synthesis.