Self-defined race/ethnicity and true underlying genetic structure

The researchers took skin reflection measurements and genotyped individuals, clustering them based on their genotypes. As observed before the number of clusters is not arbitrary but corresponds exactly to the races of traditional physical anthropology.

For the three racial/ethnic groups combined, the posterior probabilities of K obtained from Structure, Pr(X | K), were close to 1 when K = 3 and close to 0 for all other tested K values. This means that the optimal number of clusters was three.

69% of skin color variation could be explained by self-reported ancestry and there were 10 mis-assigned individuals out of 1,334. 4 of them were likely of mixed recent ethnicity. Additionally, African Americans, and Hispanics had a higher variance in skin color, as can be expected due to their multi-racial origins.

Ann Hum Genet (early view)

The role of Self-Defined Race/Ethnicity in Population Structure Control

X-Q. Liu et al.

Population-based association studies are powerful tools for the genetic mapping of complex diseases. However, this method is sensitive to potential confounding by population structure. While statistical methods that use genetic markers to detect and control for population structure have been the focus of current literature, the utility of self-defined race/ethnicity in controlling for population structure has been controversial. In this study of 1334 individuals, who self-identified as either African American, European American or Hispanic, we demonstrated that when the true underlying genetic structure and the self-defined racial/ethnic groups were roughly in agreement with each other, the self-defined race/ethnicity information was useful in the control of population structure.

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