Regarding PCR mutagenesis, I personally wouldn't want to do it [I don't think the frequency would be high enough], but if I were to try, I think I would use a dramatically lower elongation temperature [37-42C]. It still synthesizes there, it just doesn't do it very well. Ernie Retzel Dept. of Microbiology Univ. of Minnesota ernest at lenti.med.umn.edu