The Nucleus: Information Central
• The nucleus contains most of the cell’s genes and is usually the most conspicuous organelle
• The nuclear envelope encloses the nucleus, separating it from the cytoplasm
• The nuclear membrane is a double membrane; each membrane consists of a lipid bilayer
• Pores regulate the entry and exit of molecules from the nucleus (rRNA, mRNA, nucleoprotein )
• The shape of the nucleus is maintained by the nuclear lamina, which is composed of protein
• In the nucleus, DNA is organized into discrete units called chromosomes
• Each chromosome is composed of a single DNA molecule associated with proteins
• The DNA and proteins of chromosomes are together called chromatin
• Chromatin condenses to form discrete chromosomes as a cell prepares to divide
• The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis