“Modeling Assortative Mating and Genetic Similarities between Partners, Siblings, and In-Laws”, 2022-03-01 ():
assortative mating on heritable traits can have implications for the genetic resemblance between siblings and in-laws in succeeding generations.
We studied polygenic scores and phenotypic data from pairs of partners (n = 26,681), siblings (n = 2,170), siblings-in-law (n = 3,905), and co-siblings-in-law (n = 1,763) in the Norwegian Mother, Father and Child Cohort Study. Using structural equation models, we estimated associations between measurement error-free latent genetic and phenotypic variables.
We found evidence of genetic similarity between partners for educational attainment (rg = 0.37), height (rg = 0.13), and depression (rg = 0.08). Common genetic variants associated with educational attainment correlated between siblings above 0.50 (rg = 0.68) and between siblings-in-law (rg = 0.25) and co-siblings-in-law (rg = 0.09). Indirect assortment on secondary traits accounted for partner similarity in education and depression, but not in height. Comparisons between the genetic similarities of partners and siblings indicated that genetic variances were in intergenerational equilibrium.
This study shows genetic similarities between extended family members and that assortative mating has taken place for several generations.
…Because siblings provide information on the level of assortment in previous generations and partners provide information on the level of assortment in the current generation, we test whether the results are consistent with stable levels of genetic assortment across generations. The results suggest no deviations from intergenerational equilibrium, indicating that assortment on these traits has been going on for at least 5 generations and that one should not expect further genetic consequences for succeeding generations with the present level of assortment.
…Partner similarity can have genetic consequences in the following generations if the assortment is based on heritable traits, which almost all human traits are. When offspring inherit genetic variants from both parents that deviate in the same direction from the population mean, otherwise independent genetic variants can become correlated (gametic phase disequilibrium). This results in the elevated resemblance between siblings and increased genetic variation between families. Increased genetic variation translates into larger variation between individuals in phenotypic expression.