Nucleolus: The nucleolus is a round body located inside the nucleus of a eukaryotic cell. It is not surrounded by a membrane but sits in the nucleus. The denser, small and round body found in the nucleus is the nucleolus. Every nucleus normally contains a single nucleolus. Nucleolus is usually attached to a certain area of a Particular chromosome. The region of chromosome where it remains attached is called `secondary constriction’.
Chemical composition: The main compositions of the nucleolus are protein, RNA and a trace of DNA. This structure is made up of proteins and ribonucleic acids (RNA). Its main function is to rewrite ribosomal RNA (rRNA) and combine it with proteins. This results in the formation of incomplete ribosomes. Physical structure: Nucleolus is usually divided into three parts namely fibrous, granular and matrix.
Function: To synthesise various types of DNA and protein and preserve them. Chromosome: In every nucleus there are a definite number of chromosomes according to the characteristic of definite species. It can be seen under microscope after proper staining, only in a dividing cell. Every chromosome contains one or more centromere, one chromonema or more chromonemata and some chromosome may have satellite. Chromosome bears a number of gene and genes are responsible for expressing characteristics of different species.