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The word nucleus is derived from a Latin word nucleus or nuculeus which means 'kernel'. Nucleus a double-membrane bound cell organelle present in eukaryotic cells. The nucleus constitutes most of the genetic material of the cell - the DNA.
The nucleus maintains the integrity of the genes which regulate the gene expression, in-turn regulating the activities of the cell. Therefore, the nucleus is known as the control center of the cell.
Functions of the nucleus
It controls the heredity characteristics of an organism.

It is responsible for protein synthesis, cell division, growth and differentiation. 
Stores heredity material in the form of deoxy-ribonucleic acid (DNA) strands.Also stores proteins and ribonucleic acid (RNA) in the nucleolus. 
It is a site for transcription process in which messenger RNA (m RNA) are produced for protein synthesis.
Aids in exchange of DNA and RNA (heredity materials) between the nucleus and the rest of the cell.
Nucleolus produces ribosomes and are known as protein factories.
It also regulates the integrity of genes and gene expression.
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Nucleus is the largest cell structure it is a spherical or oval prominent structure,usually located in the centre of the cell.Robert brown discovered it in has nuclear membrane,nucleoplasm,chromatin material,nucleolus.
controls all metabolic activities of the cell.
it regulates the cell cycle.
it is concerned with the transmission of hereditary traits from the parent to offsprings. 
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