Married Couples with Common Ancestry Share Similar Genes.
When two married people appear similar, it isn’t necessarily a coincidence, but may be related to the tendency to marry someone with the same ancestry—a trend that can have important effects on the genetics of different populations, says a new study co-authored by School of Public Health researchers.
The study, published in PLOS Genetics, explored genetic similarities between spouses from three generations of white people in the Framingham Heart Study, an ongoing examination of the heart health of residents of Framingham, Massachusetts, which began in 1948.
Until recently, the authors noted, most people picked a spouse from within their local communities, and that person often had the same ancestry. Over many generations, this affinity for similar mates has created a genetic structure in the population that has the potential to bias the results of genetic studies.
In the first investigation into mating patterns across multiple generations within a US population, the researchers used genomic data to characterize the ancestry of 879 participant spouse pairs. They observed that individuals of Northern European, Southern European, and Ashkenazi ancestry preferentially chose spouses of the same background. In each successive generation, however, individuals were less likely to choose a spouse with the same ancestry.
The study also showed that mating patterns caused spouses to be more genetically similar to each other than might otherwise be expected, and that the genetic structure created by these mating patterns in the population has decreased over time.
The findings from the study reflect how demographic patterns have changed in the past 60 years in a community such as Framingham. Also, genetic similarity within a population can be important to consider in genomic studies because it can lead to false positives when identifying gene regions that are associated with a disease, and affect estimates of the degree to which a disease is passed on through one’s genes, the authors said.
Josée Dupuis, professor and chair of biostatistics, is a co-senior author on the study. Neil Risch of the University of California San Francisco; Ronnie Sebro of the University of Pennsylvania; and Gina Peloso, assistant professor of biostatistics, are co-authors.