ribosome@gentoo.org Olivier Fisette sci-biology Primer3 picks primers for PCR reactions, considering: oligonucleotide melting temperature, size, GC content, and primer-dimer possibilities; PCR product size; positional constraints within the source sequence; and miscellaneous other constraints. All of these criteria are user-specifiable as constraints, and some are specifiable as terms in an objective function that characterizes an optimal primer pair.