Francis Collins, who helped map the human genome, did not get around to having his own genes analysed until last summer. And he was surprised by what he learned.
Family history doesn't cost a thing
Armed with that information, he eventually lost 11kg. But as a rule, he doesn't consider such tests especially useful - at least not yet. "Admittedly, right now your family history may be your best bet and it doesn't cost anything," he said.
A personalised blood test can tell whether a patient's cancer has spread or come back. Dr Bert Vogelstein of Johns Hopkins University in Baltimore and colleagues found stretches of DNA in colon and breast tumours with extra DNA copies, or fused-together chromosomes.
A gene-based test called Oncotype DX helps identify breast cancer patients who are not likely to benefit at all from chemotherapy.
Dr James Lupski of the Baylor College of Medicine in Houston studied his own entire DNA map and sequenced the genomes of family members - including his deceased grandfather - to diagnose the mutation causing his rare genetic nerve disease, called Charcot-Marie-Tooth syndrome.
Genetic tests are now able to pick out poor responders to Plavix, or clopidogrel, a common life-saving anti-clotting drug.