As described in the journal The Public Library of Science, Evans and his colleagues created the "marathon mice" by modifying the PPAR delta gene and these furry runners provide powerful clues as to how the PPAR delta gene actually works.

FORBES: Of Marathon Mice And Fat Men

The other method of genetically modifying a natural seed is to insert into it a gene that makes the crop tolerant to a specific herbicide, usually one the company makes itself.

FORBES: Magazine Article