Nalls, M., Simon-Sanchez, J., Gibbs, J., Paisan-Ruiz, C., Bras, J., Tanaka, T., Matarin, M., Scholz, S., Weitz, C., Harris, T., Ferrucci, L., Hardy, J., & Singleton, A. (2009). Measures of Autozygosity in Decline: Globalization, Urbanization, and Its Implications for Medical Genetics PLoS Genetics, 5 (3) DOI: 10.1371/journal.pgen.1000415

The study, published in the latest issue of PLoS Genetics, used genome-wide patterns of genetic variation in 809 unrelated American males to explore changes in the degree of inbreeding in the North American population over the last century. Inbreeding leaves a characteristic signature in the genome: long tracts of autozygosity, meaning regions in which an individual has inherited the same sets of genetic variants from both parents. The more closely-related an individual’s parents are the more of these regions they will carry and the longer such regions will be.

The authors of this study took advantage of a set of healthy individuals collected by the Coriell Institute as a generic control group, sampled so as to be broadly representative of the North American population of varied European descent. The cohort contained individuals ranging from 19 to 99 years of age, essentially providing a sliding window of patterns of genetic change over the last century. Because the cohort was used as a control in genome-wide association studies the researchers had access to information from over half a million genetic variants scattered throughout the genome of each participant.

That dataset allowed the authors to directly measure the levels of autozygosity and estimate changes in the level of inbreeding over the last hundred years. Here’s the money shot: