5. Nucleus

Robert Brown coined the term nucleus in 1831. It is a double membrane-bound dense protoplasmic body. It encompasses the genetic information of the cell, i.e., the genetic material (DNA or RNA of the Cell). It is absent in prokaryotes, mature RBCs and mature sieve cells of vascular plants.

 

Based on the number of nuclei, a cell can be classified as uninucleate, binucleate or multinucleate.

 

Nucleus' shape is spherical or elliptical in most of the cases. It encompass a liquid ground substance called nucleoplasm. It contains nucleolus and chromatin material.

 

Nucleolus is almost like a round structure that is found inside the nucleus. There is no covering membrane for it. It is termed as a factory of ribosomes.

 

Chromatin is a bunch of long thread-like structures found inside the Nucleus. It is composed of DNA and proteins that condense to form chromosomes. Whenever the cell involves in Cell division, the chromatin material gets organized into rod-shaped structures of chromosomes. Chromosomes contain information that inherits characters from parents to the next generation in the form of DNA (Deoxyribonucleic acid).

 

Functional units of DNA are called genes. The DNA molecules possess enough information for constructing and organizing the cells. Nucleus also contains RNA (Ribonucleic acid), which directs the synthesis of a protein molecule.

 

In few organisms like bacteria, the nuclear region of the cell is not fully developed due to the absence of a double-layered covering membrane. In those cases, only nucleic acid is present in the nuclear region. Such an undeveloped nuclear region is called nucleoid.

 

1. Is the shape of the chromosome is rod shape?

 

2. Given an example of organism which don't have nucleus?

 

3. What are the two main components present inside the Nucleoplasm?