Restriction endonucleases are the enzymes, which cut a DNA molecule within certain specific sites that have specific base sequence, eg, Hae-III, Eco-RI, Bam-II, Hind-Ill, Pst-I, etc. DNAse-I is not a restriction endonuclease enzyme. DNA polymerase-III synthesizes DNA, while DNA polymerase-I erases primer and fills gaps during DNA replication.