Nucleus discovery funtion its chemical composition and variation in animals regarding number of nucleus

Nucleus

Discovery

Nucleus was first reported by Robert brown in 1831. It was prominent in many cells so its discovery was undoubted.

Function

It controls and maintains the life, activities and function of cells.

Location

It is located at centre of cell in animal cell, while in plants due to presence of large centre vacuole it is pushed towards periphery.

                                             

Variations regarding number of nucleus

·         Mononucleated cells have one nucleus

·         Binucleated cells have two nucleus

·         Multinucleated cells have more than two nucleuses in it.

Nucleoplasm and chromatin network

The soluble sap of nucleus is called nucleoplasm which contain chromatin network that is undifferentiated. This chromatin material is disappeared and replaced with thread like structure called chromosomes during cell division.

Chemical composition

DNA, RNA and protein consisting of enzymes form the chemical composition of nucleus.

Structure of nucleus

Nuclear membrane

Nucleus is double membranous structure that is a nuclear envelop. Nuclear contents are enclosed in inner membrane while endoplasmic reticulum is continues with outer nuclear membrane.

Nuclear pores

These are the points at which the outer and the inner nuclear membranes make connection. The exchange of materials between nucleus and cytoplasm is allowed by these pores. The number of these pores may vary from nucleus to nucleus.

Nucleolus

In nucleus, the darkly stained body is called nucleolus.  No membranous boundary is present around. It is the factory for synthesize of RNA and to store it.

Chromosomes

Chromatin material is replaced with thread like structure called chromosomes that is highly stained. Chromosomes consist of arms and centromere. During cell division, spindle fibers are attached at the place called centomere. Each chromosome consist of two identical chromatids known as sister chromatids.

                                            

DNA and protein forms the composition of chromosomes. Genes are located at chromosomes which control activities of cell and transfer information from generation to generation. The number of chromosomes varies from specie to specie as;

ü  Frog has 26.

ü  Drosophila has 16.

ü  Chimpanzee has 48.

ü  Fruit fly has 8.

ü  Human has 46.

ü  Garden pee has 14

ü  Potato has 48.