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摘要

Tiny changes in DNA can have huge consequences. For years, scientists have been trying to 'fix' these mutations in the hope of treating and potentially curing some of humanity's most devastating genetic diseases. After some tragic early setbacks (see Nature 420,116-118; 2002), techniques that allow precise genetic manipulation have created a surge of research. Although most existing treatments for genetic diseases typically only target symptoms, genetic manipulation or gene therapy' goes after the cause itself. The approach involves either inserting a functional gene into DNA or editing a faulty one that is already there, so the conditions most likely to prove curable are those caused by a single mutation. Sickle-cell disease is a perfect candidate: it is caused by a change in just one amino acid at a specific site in the β-globin gene. This results in the production of abnormal haemoglobin proteins that cause the red blood cells that house them to twist and become sickle shaped. The distorted cells get sticky, adhere to each other and block blood vessels, preventing oxygenated blood from flowing through.