The nucleus is the control centre of the cell. It contains a stable number and type of chromosomes. Chromosomes are the most important substance in the cell because they are the carriers and bearers of genetic materials. The most important chemical component of the chromosomes is   the nucleic acid

Nucleic acid occur in chromosome in the form of (DNA) deoxyribonucleic acid and ribonucleic acid (RNA)

DNA is the only genetic material in the chromosomes and each species is characterized by its own specific type of DNA. The functional unit of the DNA is the gene which is capable of directing the synthesis of specific type of proteins