 DNA POLYMERASE  DNA POLYMERASE I : (KORNBERG ENZYME) 6 Important function of this enzyme is 5'  3' polymerization. It has exonuclease activity in both 5'  3' and 3'  5' direction It removes RNA primer through 5'  3' exonuclease activity and replace it with the nucleotide of DNA and can correct the thymidine dimer (T = T) formed under the influence of UV-rays. Also takes part in repair replication. DNA POLYMERASE II: It takes part in polymerization from 5'  3' direction. Its polymerization speed is less, i.e., only 50 nucleotide per minute. It performs a supporting role over the activity of other DNA polymerases. DNA POLYMERASE III: It performs 5'  3' polymerization. It is the most important or main polymerizing enzyme having a great polymerization speed (about 2000 bp per second).  DNA polymerase II & III have only 3'  Kornberg (1956), succeeded in demonstrating the in vitro synthesis of DNA molecule using a single strand of DNA as a template. He extracted and purified an enzyme from E. coli which was capable of linking free DNA nucleotides, in presence of ATP as an energy source, to form complementary strand. He called it DNA polymerase. DNA 5' exonuclease activity. polymerase-I is called Kornberg enzyme.  In eukaryotes DNA polymerases are of 5 type these are DNA polymerase , , , , .In eukaryotes, the replication of DNA takes place at s-phase of the cell cycle. The replication of DNA and cell division cycle should be highly co-ordinated. A failure in cell division after DNA replication result into polyploidy (achromosomal anomaly).