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Chunk #21 — Materials and Methods — SNP Genotyping and Quality Control

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Haplotypes with copy number and single nucleotide polymorphisms in CYP2A6 locus are associated with smoking quantity in a Japanese population.
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SNP genotyping was performed using the Illumina HumanHap610-Quad Genotyping BeadChip (Illumina, CA, USA) for the GWAS, which was conducted for 19 diseases (Table S1). After excluding subjects with call rates lower than 0.98, we excluded SNPs with call rates lower than 0.99, SNPs with ambiguous calls, and non-autosomal SNPs. We also excluded closely related subjects using IBS. For each pair with 1st or 2nd degree kinship, we excluded the individual with lower call rates. We also excluded subjects whose ancestries were estimated to be distinct from the other subjects using PCA performed by EIGENSTRAT (version 2.0). We performed PCA on the SNP genotype data from our study along with the genotype data from unrelated European (CEU), African (YRI), and East-Asian (Japanese and Han Chinese; JPT + CHB) individuals obtained from the Phase II HapMap database (release 24). Based on the PCA plot, we excluded subjects who fell outside the JPT and CHB clusters (Figure S1). We then excluded SNPs with a MAF of or SNPs with Hardy-Weinberg equilibrium (HWE) test P-value (Fisher's exact test). Ultimately, we obtained genotype data on