Features

• Transgenic crops are widespread in the United States; according to the U.S. Department of Agriculture, for example, about 93 percent of soybeans grown today are genetically modified (GM). Transgenic crops have been altered by splicing a gene from another organism into their genome so that they possess a desired trait; the plant will still reproduce like any other plant, and seeds from GM plants will grow unless modified to do otherwise.
  
  

Function

• Many transgenic plants today feature genetic-use restriction (GURT) or terminator technology. In the most popular form of GURT, three additional genes are added to the plant's genome. The first gene produces a protein that terminates seed development; this gene is disabled with a blocking sequence, however, so it's only active once the blocking sequence is excised. The second gene codes for a recombinase that will excise the blocking sequence. The third gene codes for a repressor that switches off the second gene.
  
  

Effects

• Plants with GURT develop and reproduce normally, since the third gene is active and prevents the second and first genes from being expressed. Spraying with a specific chemical turns off the third gene; the second gene then becomes active and switches on the first gene so that seeds from the plant "self-destruct" and never develop. This technology forces farmers to buy seeds from the company each year and protects the company's investment. For this reason, terminator technology has become somewhat controversial.