Each year, millions of people in the United States get a tuberculosis skin test to see if they have the infection that still affects one-third of the world’s population. But the standard diagnostic test is difficult to give, because a hypodermic needle must be inserted at a precise angle and depth in the arm to successfully check for tuberculosis.

The slightest variation in a sequence of DNA can have profound effects. Modern genomics has shown that just one mutation can be the difference between successfully treating a disease and having it spread rampantly throughout the body.