Contains 0.25 ml of 100 mM ultrapure dUTP. dUTP can either be fully substituted for dTTP or added in addition to conventional dNTPs. dUTP can be used with Family A polymerases (such as Taq) or modified Family B polymerases, such as Q5U Hot Start High-Fidelity DNA Polymerase. Q5U contains a mutation in the uracil-binding pocket that enables the ability to read and amplify templates containing uracil and inosine bases. For a simplified protocol, dUTP can be added to most polymerase reactions at the same concentration as other nucleotides (e.g., a 1:1:1:1:1 dA/dC/dG/dT/dU ratio). For applications that require other molar ratios (up to and including full substitution of dU for dT), custom nucleotide mixes must be made. We recommend starting with a concentration of 0.2 mM of each dNTP for both Taq and Q5U DNA polymerases.