DNA is the carrier of genetic information in all cells and in many viruses. It stores the complete genetic information required to specify the structure of all the proteins and RNAs of each species of organisms. It programmes in time and space the orderly biosynthesis of cell and tissue components determines the activities of an organism and it determines the individuality of a given organism.

RNA is the link between DNA and enzymes. It is associated with the process of protein synthesis which expresses genetic information. It is found in cytoplasm, both in soluble form (sRNA)and associated with ribosomes. It also occurs in the nucleolus.