What enzyme connects new nucleotides and proofreads them in separated dna strands?

DNA polymerase is the enzyme that connects new nucleotides and proofreads them into separate DNA strands. 

This process is part of DNA replication. A cell's DNA is replicated before a cell divides. The two strands of a DNA molecule have complementary base pairs. Each strand in the pair consists of a nucleotide sequence which is able to provide the information to duplicate itself. Before the duplication occurs, the length of the DNA that is about to be copied must be unwound and the two strands must be separated. This is done by breaking the weak hydrogen bonds that link the pairs together. They must then be kept apart from each other to expose the bases so that the new nucleotide partners can bond to them. DNA polymerase is the enzyme that moves along the exposed DNA strand and joins the new nucleotides to manufacture a new DNA strand that is a duplicate of the original