T4 DNA polymerase is a DNA polymerase derived from the T4 bacteriophage, typically extracted from Escherichia coli (E. coli) that carries its gene. In the presence of a template and primer, T4 DNA polymerase can synthesize DNA in the 5'→3' direction. Additionally, it possesses 3'→5' exonuclease activity but lacks 5'→3' exonuclease activity. T4 DNA polymerase is widely used in molecular biology experiments, particularly for applications such as DNA end smoothing and gap filling.