Gene duplications are scattered widely throughout the human genome. A single-base difference located in nearly identical duplicated segments may be misjudged as a single nucleotide polymorphism (SNP) from individuals. This imperfection is undistinguishable in current genotyping methods. As the next-generation sequencing technologies become more popular for sequence-based association studies, numerous ambiguous SNPs are rapidly accumulated. Thus, analyzing duplication variations in the reference genome to assist in preventing false positive SNPs is imperative. We have identified >10% of human genes associated with duplicated gene loci (DGL). Through meticulous sequence alignments of DGL, we systematically designated 1,236,956 variations as duplicated gene nucleotide variants (DNVs). The DNV database (dbDNV) (http://goods.ibms.sinica.edu.tw/DNVs/) has been established to promote more accurate variation annotation. Aside from the flat file download, users can explore the gene-related duplications and the associated DNVs by DGL and DNV searches, respectively. In addition, the dbDNV contains 304,110 DNV-coupled SNPs. From DNV-coupled SNP search, users observe which SNP records are also variants among duplicates. This is useful while ?58% of exonic SNPs in DGL are DNV-coupled. Because of high accumulation of ambiguous SNPs, we suggest that annotating SNPs with DNVs possibilities should improve association studies of these variants with human diseases.
