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Did You Know?

You have more in common with your best friend or a chimp than you might think. Scientists estimate that 99.9 percent of the DNA of most humans is identical. Your genetic differences in physical appearance, behavior, or biochemistry (such as a tendency for a particular illness) account for only 1/1,000 of your DNA. In fact, when it comes to genes, chimps and humans are about 98 percent identical.

Geneticists have created a potato that can self destruct. This potato's enemy is a fungus that can destroy an entire crop. To help combat the problem, genetic engineers created a potato that has a "self-destruct switch." If the fungus attacks one of these potatoes, it sacrifices itself and takes the fungus with it, preventing the fungus from spreading. Genetic engineers created this potato by copying the fungus' gene for an enzyme called barnase. Then they placed that gene into the potato's DNA. If the fungus attacks the potato, its own gene kills it before it can cause any more damage.

Identical twins aren't completely identical. About one-third of all twins are monozygotic, or identical, meaning they came from a fertilized egg that separated into halves. These twins, who have the same chromosomes and DNA, usually look very much alike. But no one in the world has the same fingerprints, not even identical twins. Besides fingerprints, physical differences in identical twins may include height and weight.

A genetic blood disorder can make your skin look blue. Methemoglobinemia is a rare disorder that is passed from generation to generation. It creates excessive amounts of methemoglobin, a blue form of the red hemoglobin that carries oxygen. People with this disorder can accumulate so much methemoglobin that it overwhelms the red color in normal hemoglobin. Their bluish complexions may not always appear, but the blue in their skin usually darkens when they are cold, sick, or under stress. Because the trait is recessive, both parents must carry the gene for a child to be born with blue skin. But even descendants of one parent with the gene can have a bit more blue in their skin.