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. 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. 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. 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 :
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.
Nuclear Lamina: This protein meshwork, located beneath the inner nuclear membrane, provides structural support and helps maintain the shape of the nucleus.
Nucleolus: This is a spherical body within the nucleus responsible for producing ribosomes, which are essential for protein synthesis.
Chromatin: This is the DNA and protein complex that makes up the chromosomes. During cell division, chromatin condenses into visible chromosomes.
Nucleoplasm: This is the gel-like substance within the nucleus that suspends the other nuclear components, including the nucleolus and chromatin.
Explain the molecular mechanism by which nuclear pore complexes (NPCs) regulate selective transport of macromolecules across the nuclear envelope.
How does the spatial organization of chromatin within the nucleus influence gene expression and genome stability?
Describe the role of nuclear lamins in nuclear integrity and their involvement in laminopathies.
How is the cell cycle regulated by nucleocytoplasmic transport of key transcription factors like p53 and NF-κB?
What are the differences in the composition and function of the nucleoplasm versus the cytoplasm, and how do they impact RNA processing?
Explain the dynamic changes in the nuclear envelope during mitosis and how they are coordinated with chromosomal behavior.
How does the nucleolus participate in ribosomal RNA processing and what are the implications of nucleolar stress?
Describe the role of small nuclear RNAs (snRNAs) and small nucleolar RNAs (snoRNAs) in nuclear RNA splicing and modification.
What is the functional significance of nuclear bodies (like Cajal bodies, PML bodies) and how do they contribute to gene regulation?
How do post-translational modifications of histones in the nucleus influence epigenetic gene regulation?
What is the mechanism of nuclear import and export involving karyopherins and Ran-GTP gradients?
Explain how nuclear localization signals (NLS) and nuclear export signals (NES) function at the sequence and structural level.
Describe the molecular steps and regulation of pre-mRNA splicing in the nucleus.
How do nuclear receptors like estrogen and glucocorticoid receptors modulate transcription upon ligand binding?
In what ways do mutations in nuclear components contribute to diseases such as Hutchinson-Gilford progeria syndrome (HGPS)?