DNA, the molecular chip of a cell, occupies a unique place among all the biological macromolecules, because it is considered the blueprint of an organism. The nucleotide sequence of DNA carries all the necessary information for forming the primary structures of all cellular RNAs and proteins. By encoding the enzymes, DNA indirectly affects the synthesis of all other cellular constituents. The information stored in DNA in the form of nucleotide sequence is transmitted from one generation of cells to the next without any error and in an uncorrupted state. The formulation of the structure of DNA by Watson and Crick in 1953 was accompanied by a proposal for its self-duplication. The process of DNA duplication is called ‘replication’, a biological process that occurs in all living organisms prior to cell division. The process of replication results in the production of two identical daughter DNAs originally copied from the parent DNA. Each strand of DNA double helix can serve as template for the synthesis of a new strand to form duplicated DNA. Watson and Crick proposed that the replication of DNA involves breakdown of weak hydrogen bonds that hold the duplex together and the process is followed by rotation and separation of both the polynucleotide strands. Each separated strand acts as a template as it contains the information required for the synthesis of the other strand. Each base of the template strand attracts the complementary nucleotide available within the cell and thus produces the replicas of the double helical molecule.
INTRODUCTION