A bioinformatic filter for improved base-call accuracy and polymorphism detection using the Affymetrix GeneChip® whole-genome resequencing platform

Pandya, Gagan A.; Holmes, Michael H.; Sunkara, Sirisha; Sparks, Andrew; Bai, Yun; Verratti, Kathleen; Saeed, Kelly; Venepally, Pratap; Jarrahi, Behnam; Fleischmann, Robert D.; Peterson, Scott N.

The footprint effect filter algorithm assumes that a genuine SNP is most likely to cause spurious SNP calls at locations within 10 bases on either side of the genuine SNP. Any SNP call that occurs more than 10 base positions from the nearest neighboring SNP call is assumed to be valid, and any SNP call that has one or more neighbors within 10 base positions is subjected to the filter. Since any number of consecutive SNP calls within 10 base positions of each other may occur in the data, this filter is implemented as a recursive algorithm. For each list of consecutive SNP calls that each lies within 10 bases of its neighbors, the algorithm identifies the SNP call having the highest quality score. That SNP call is accepted as valid, and its immediate neighbors are removed from the list of high-confidence SNP calls. This action may break the original list of neighboring SNP calls into two separate lists. All resulting lists are processed recursively in the same way, until all of the SNP calls have been accepted or rejected. This algorithm is implemented in the RemoveFootprintEffect.pl Perl program.