Transgenic silkworms could be even more productive. Breeding them involved some sneaky DNA, however. Kraig Biocraft Laboratories Inc., a Lansing, Mich., firm, partnered with Fraser, who discovered and patented a DNA transposon called "piggyBAC." The transposon can insert itself into a cell's genetic material. The researchers used piggyBAC to incorporate snippets of spider DNA into silkworm embryos, resulting in silkworms that spin a hybridized part-silkworm, part-spider silk.