DNA polymerase is the chief enzyme of DNA replication. Its activity was first demonstrated by Kornberg in 1956. It catalyses the covalent addition of deoxyribonucleotides to the 3’-OH of a pre existing nucleotide called as primer. DNA polymerase-I enzyme is now considered to be a DNA repair enzyme rather than a replication enzyme. This enzyme is known to have five active sites, namely template site, primer site, 5’-3’ cleavage or exonuclease site, nucleoside triphosphate site and 3’-5’ cleavage site. DNA polymerase I is mainly involved in removing RNA primers from okazaki or precursor fragments and filling the resultant gaps due to its 5’-3’ polymerizing capacity.