Genomics has made significant inroads into mainstream medicine — DNA data are now routinely used to tailor cancer treatments, for example. But the reference genome created by the Human Genome Project, which has underlain so many of the scientific and clinical advances of the last 20 years, was never really finished. Technology at the time couldn’t resolve the last 8% — vast gaps spread across the genome that together add up to the equivalent of missing an entire chromosome.
If you imagine a world map, that’s about the size of Africa. That means doctors have always been flying with a sizable blindspot. If a patient has a disease-causing mutation in any of those portions of the reference genome that are missing or contain errors, there’s no way to test for it.