An engineered double-strand specific DNA endonuclease, dsDNase preferentially degrades double-stranded DNA (dsDNA) over single-stranded DNA (ssDNA) or RNA. This specificity toward dsDNA allows the enzyme to degrade contaminating dsDNA while maintaining the integrity of single stranded DNA molecules such as primers and probes within PCR mixes, allowing for efficient decontamination of PCR master mixes. Moreover, dsDNase displays the unique property of cleaving the DNA strand of a DNA:RNA hybrid duplex.