Adrian Vella, MD,  with Mayo Clinic, wanted to understand why some adults have high blood sugar (glucose) but never develop diabetes while others do. To understand this phenomenon, Dr. Vella had been trying for years, without success, to find patients with uncommon variants of a diabetes-associated gene called TCF7L2. Humans can carry different variants of TCF7L2 in theirDNA — one that helps protect against diabetes and one that predisposes people to the disease. To understand how these variants work, Dr. Vella needed to find a lot of people with both types of variants. Using samples from just one biobank would not yield the numbers he needed. But Mayo’s biorepository that stores samples from more than 100 biobanks allowed him to search a much larger number of DNA samples and he quickly found what he needed.