Another dataset used here is the genotype of a non-synonymous SNP in IFIH1 gene on chromosome 2, also collected by NARAC. IFIH1 gene has recently been shown to be associated with type 1 diabetes (Smyth et al., 2006), but its association status with rheumatoid arthritis is unknown. This dataset consists of 1344 independent control samples and 1328 case samples distributed in 653 pedigrees – including 67 singletons, 512 affected relative-pairs (the majority are affected sibpairs), 64 affected triples (most are sibship with 3 affected sibs), 8 affected quadruples, and two pedigrees with 5 and 8 affecteds. The three genotype counts of this SNP are listed in Table 5.
