Since humans first began domesticating crops, they have altered the genetic makeup of those plants through selection. This selection has been continuous for most of the 10,000-year history of domestication of crops, but it has accelerated over the past two centuries. In most cases, the plant species being selected have hybridized with wild and weedy races and related species, and this hybridization has enhanced the variability of the crops and, hence, the genetic material available for selection. Historically, this genetic material has come from the crop species themselves and from those related races and species capable of crossing directly with them. More recently, however, special methods of hybridization have been developed that widen the circle of species that can be included, as appropriate methods (e.g., embryo culture) have become available. Since the first experiments were successfully performed in 1973, it has also become possible to transfer genes to a recipient organism (like a crop) from any species, regardless of the degree of phylogenetic relationship. Such introduced genes are known as 'transgenes,' and the organisms to which they have been transferred as ‘genetically modified organisms' (GMOs). GMOs and ingredients derived from them are becoming part of an increasing number of products, including foods and food additives, beverages, drugs, and fuels. Genetic modification is being promoted as a way to improve crops and produce medicines, but it has raised concerns about potential side effects on human health and the environment, including risks to biological diversity. |
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