- Wang H, Haiman C, Kolonel L, Henderson B, Wilkens L, Le Marchand L, et al. Self-reported ethnicity, genetic structure and the impact of population stratification in a multiethnic study. Hum Genet. 2010;128:165-77 pubmed publisher..The bias may be large in case-only analysis of gene by gene interactions but it can be corrected by top PCs derived from all SNPs. ..