> The analysis done by Kong and his student relies on the key idea that a genetic sequence that occurs more frequently in participants than in nonparticipants will also occur more frequently in the genetic regions that are shared by two related participants.
> Put differently, a bit of DNA that is common in the population will show up frequently in the study. But it will still only have a 50/50 chance of showing up in the child of someone who carried a copy. If a bit of DNA makes people more likely to enroll in genetic studies, it will be more common both in the overall data and among closely related family members.
> So they checked the genetic sequences shared between first-degree relatives—either parents and children or siblings (but not twins)—in the UK Biobank.