THE EFFECT OF FORMALIN FIXATION ON RESTRICTION-ENDONUCLEASE DIGESTIONOF DNA AND PCR AMPLIFICATION

The effect of formalin fixation on DNA and on polymerase chain reactio n (PCR) amplification was investigated. Lambda phage DNA fixed in buff ered formalin showed incomplete digestion on restriction endonuclease treatment. The resistance to restriction digestion was dependent on th e temperature of fixation, but not affected by salt concentration of t he fixative. Lambda phage DNA fixed in unbuffered formalin showed poor PCR amplification due to degradation of DNA during fixation. Lambda p hage DNA fixed in buffered formalin evaded degradation and suited for template of amplification. Feasibility of formalin-fixed tissues as so urces for PCR amplification was also investigated with primers produci ng 128 bp fragment of c-Ki-ras exon 2. Although DNA from tissues fixed for 3 months showed amplification, there was no amplification from ti ssues kept in unbuffered formalin for longer than 6 months.