Giedre (left) and Tal Cohen in March 2013, while Giedre was still healthy. Since then, she's begun having symptoms of Alzheimer's disease. In Giedre's case, the illness is tied to a rare genetic mutation she inherited. Courtesy of Tal Cohen hide caption

itoggle caption Courtesy of Tal Cohen

Sequencing the genes of a cancer cell turns up lots of genetic mutations — but some of them are harmless. The goal is to figure out which mutations are the troublemakers. Kevin Curtis/Science Source hide caption

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After genetic testing revealed a heightened risk for breast cancer, Angelina Jolie had a precautionary double mastectomy. Alastair Grant/AP hide caption

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Angelina Jolie's decision to have a double mastectomy after genetic testing has prompted a discussion about which other tests should be covered. WPA Pool/Getty Images hide caption

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Each strand of DNA is written in a simple language composed of four letters: A, T, C and G. Your code is unique and could be used to find you. hide caption

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Should a high school student building a DNA model also have his genetic code tested for disease risks? hide caption

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