<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd"> <pkgmetadata> <herd>sci-biology</herd> <longdescription> 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. </longdescription> </pkgmetadata>