Appetizer
Most all food comes from plants – either directly by eating them or indirectly from animals that eat them. Plants we eat haven’t always looked the way they do today. See on the left how modern corn has changed from its ancestor. This is because people have selected plants for thousands of years that are sweeter, bigger, tastier and able to fight off pests and survive harsh environments.
One way people have done this uses selective breeding. Male cells, or pollen, from one plant is crossed with female cells, or eggs, of another related plant. Plants from that cross are observed and ones with the best traits are selected. For example, if we cross one tomato variety with deeper color and more vitamins with another that is sweeter, we look through resulting plants for one with sweeter, darker red, more nutritious tomatoes.
About half of the genes in each parent’s genome end up in offspring, but the choice of which genes is random. This is why two brothers look different from each other. Results with plant breeding are the same. Breeders can’t control what genes end up in a given plant. They can just choose plants with desired traits.
Today new tools speed breeders’ jobs. By developing road maps for the genome showing locations with valuable traits, breeders perform marker assisted breeding. Using this tool breeders can identify plants with specific traits using molecular markers. Think of this in terms using a word processing system to find particular words in a document.
Although selective breeding results in genetic modification, it can't be used to move traits from different kinds of organisms, like from apples to tomatoes. This kind of modification is possible using new genetic tools, called by some biotechnology, but by others genetic engineering or recombinant DNA.
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