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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For someone 2.5 inches shorter than average, the risk of coronary artery disease increases by about 13.5 percent, scientists found. PW Illustration/Ikon Images/Corbis hide caption

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There's a widely held assumption that a slight imbalance in male births has its start at the very moment of conception. But researchers say factors later in pregnancy are more likely to explain the phenomenon. CNRI/Science Source hide caption

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Glenn Lightner in 2012 at age 13. His father searched clinicaltrials.gov for years, to no avail, hoping to find a promising experimental cancer treatment that might save his son's life. Courtesy of Lawrence Lightner hide caption

itoggle caption Courtesy of Lawrence Lightner

It's a good start when experimental compounds stop the proliferation of cancer cells in the lab. But, as many researchers have learned the hard way, that's just an early step toward creating a worthwhile treatment. Science Source hide caption

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Dr. Margaret Hamburg will have served almost six years as FDA commissioner by the time she leaves, far longer than the recent tenure for chiefs of the agency. J. David Ake/AP hide caption

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A nurse administers an experimental Ebola vaccine Monday at Redemption Hospital in Monrovia, Liberia. Researchers aim to give shots to 27,000 people during the large trial. John Moore/Getty Images hide caption

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Harvard University student Elana Simon introduces President Obama before he spoke at the White House Friday about an initiative to encourage research into more precise medicine. Mandel Ngan/AFP/Getty Images hide caption

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Augustine Goba (right) heads the laboratory at Kenema Government Hospital in Sierra Leone. He and colleagues analyzed the viral genetics in blood samples from 78 Ebola patients early in the epidemic. Stephen Gire/AP hide caption

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Scientists reprogrammed the common bacterium E. coli so it requires a synthetic amino acid to live. BSIP/UIG via Getty Images hide caption

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Dr. Stephen Teach helps Jeffery Ulmer listen to his daughter Alauna's asthmatic breathing at Children's National Medical Center in Washington, D.C. Alauna's mother, Farisa, holds her. The District has one of the highest rates of pediatric asthma in the country. Jahi Chikwendiu/Washington Post hide caption

itoggle caption Jahi Chikwendiu/Washington Post