Introduction

• Nucleus, A membrane bound organelle in most of the Eukaryotic Cells, is a storage of genetic information and chromosome. Nucleus does not exist in some Eukaryotic Cells, like RBC and it exists more that 1 in some other Eukaryotic Cells, like Osteoclasts.

• The nucleus in a cell performs three primary functions: 1) storing the cell's genetic information (DNA), 2) regulating gene expression through transcription, and 3) copying DNA during replication. 

• Here's a more detailed explanation:

  1. 1. Storing DNA : The nucleus houses the cell's DNA, which is organized into chromosomes and contains the instructions for cell growth, development, and reproduction, as well as directing protein synthesis. 

  2. 2. Regulating Gene Expression: The nucleus controls which genes are turned on or off, determining which proteins are produced. This process, called transcription, involves copying DNA into RNA, which then leaves the nucleus to guide protein synthesis in the cytoplasm. 

  3. 3. DNA Replication: The nucleus is also the site where DNA is duplicated during cell division, ensuring that each new daughter cell receives a complete set of genetic instructions. 

Structure

• In mammalian cells, the average diameter of the nucleus is approximately 6 mm, which occupies about 10% of the total cell volume.

• 5 Major Parts of a Nucleus :

  1. Nuclear Envelope: This double-layered membrane encloses the nucleus and separates it from the cytoplasm. It's continuous with the endoplasmic reticulum and contains nuclear pores that regulate the movement of molecules in and out of the nucleus. 

  2. Nuclear Lamina: This protein meshwork, located beneath the inner nuclear membrane, provides structural support and helps maintain the shape of the nucleus. 

  3. Nucleolus: This is a spherical body within the nucleus responsible for producing ribosomes, which are essential for protein synthesis. 

  4. Chromatin: This is the DNA and protein complex that makes up the chromosomes. During cell division, chromatin condenses into visible chromosomes. 

  5. Nucleoplasm: This is the gel-like substance within the nucleus that suspends the other nuclear components, including the nucleolus and chromatin.