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From cucumbers and carrots to white rice and wheat, we humans have altered the genes of almost every food we eat. For almost 10,000 years we've been engineering plants by keeping the seeds from the best crops and planting those the next season. Following this practice year after year has resulted in a slow but steady change -- and a substantial cumulative effect. We've been altering the genetic makeup of crops by cross-pollinating, too. About 8,000 years ago, for example, farmers in Central America crossed two mutant strains of a weedy-looking plant called Balsas teosinte and produced the first corn on the cob.
We've had success with the methods mentioned above (especially cross-pollinating), but because they rely on the random mixing of all of a plant's tens of thousands of genes, the odds of producing a crop with a desired trait is akin to winning a lottery. Today scientists can produce a change quickly by selecting a single gene that may result in a desired trait and inserting that gene directly into the chromosome of an organism. Amazingly, genes from organisms as dissimilar as bacteria and plants can be successfully inserted into each other.
These activities let you compare the traditional method of selective breeding with one of the latest transgenic methods.
wheat photograph ©h. david sewell/corbis
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