U.S. flag

An official website of the United States government, Department of Justice.

DNA Amplification for Forensic Analysts

Buffer and MG2+

Home  |  Glossary  |  Resources  |  Help  |  Contact Us  |  Course Map


Reaction pH can alter the fidelity of an insertion. A 10-50µM Tris-HCl buffer with a pH between 8.3 and 8.8 (when measured at 20°C) is used.11


The magnesium concentration may affect all of the following:11

  • Primer annealing
  • Strand disassociation temperatures of template
  • Strand disassociation temperatures of PCR product
  • Product specificity
  • Formation of primer-dimer artifacts
  • Enzyme activity and fidelity

In general, increasing the free magnesium concentration increases yield and decreases specificity and fidelity.

Taq DNA polymerase requires free magnesium (0.5 to 2.5mM) additional to that bound by template DNA, primers, and dNTPs. The presence of EDTA or other chelators in the primer stock or template DNA might disturb the apparent magnesium optimum.

Back Forward