NUCLEUS

Nucleus is the largest centrally located cell organelles which contain genetic material of the eukaryotic cell.

• It is covered by nuclear membrane.
• Nuclear membrane separates the nucleus from cytoplasm.
• There are many pores in the nuclear membrane called nucleopores.
• Nucleopores allow transportation of substance from nucleoplasm to cytoplasm and vice versa.
• It is known as the brain of cell.
• In nucleoplasm there are two types of substances are present:-

1. Nucleolus
2. Chromatin material or genetic material

NUCLEOLUS

• It is present inside in the nucleus.

• It is the site of ribosome formation.
• It is rich in protein and RNA.
• It is known as Factory of ribosome.
• Ribosome is used in protein synthesis in cytoplasm.

Chromatin material

• Chromatin material is made up of :-

1. DNA
2. Histones peotein

• Chromatin is made up by joining lots of nucleosome.
• The DNA wrap on histone protein to formed nucleosome.
• These chromatin is condensed during cell division to form chromosome.
• DNA contains all the information about cell or organism.
• The segment of DNA which contain information about one character is called gene.

Chromosome

• Chromosome is thread like structure present in nucleus seen only at the time of cell division.
• It contains hereditary information.

Structure of chromosome

• There is two arms in Chromosome one is short and another one is long.
• Both the arm is attached with centromere (primary constriction).
• The terminal region of both the arm is called telomare.

• The chromosome is seen during cell division.
• Before cell division there is replication of chromosome takes place.
• The two copies of chromosomes attached to the same centromeres and both the copy is called sister chromatid.
• During cell division both the chromatid will seprates and become a independent chromosme.

Function of nucleus

• Controls hereditary characteristics of organism.
• Controls all the metabolic activities in the cell.
• Regulates the cell cycle.

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