Comparison of ethnicity in each of the sample series. The first 2 principal components of the analysis were plotted based on genotypes from 6000 randomly selected SNPs. HapMap persons are plotted in gray. CEU indicates Utah residents with ancestry from northern and western Europe (far left); CHB + JPT, Han Chinese in Beijing, China; Japanese in Tokyo, Japan (bottom right); YRI, Yoruba in Ibadan, Nigeria (top right): (A) UKCCS BCP-ALL cases, (B) Northern Institute of Cancer Research and United Kingdom MRC BCP-ALL cases, (C) 1958 birth cohort controls, and (D) colorectal cancer controls.