Learning Significant Alignments: An Alternative to Normalized Local Alignment

  • Authors:
  • Eric Breimer;Mark Goldberg

  • Affiliations:
  • -;-

  • Venue:
  • ISMIS '02 Proceedings of the 13th International Symposium on Foundations of Intelligent Systems
  • Year:
  • 2002

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Abstract

We describe a supervised learning approach to resolve difficulties in finding biologically significant local alignments. It was noticed that the O(n2) algorithm by Smith-Waterman, the prevalent tool for computing local sequence alignment, often outputs long, meaningless alignments while ignoring shorter, biologically significant ones. Arslan et. al. proposed an O(n2 log n) algorithm which outputs a normalized local alignment that maximizes the degree of similarity rather than the total similarity score. Given a properly selected normalization parameter, the algorithm can discover significant alignments that would be missed by the Smith-Waterman algorithm. Unfortunately, determining a proper normalization parameter requires repeated executions with different parameter values and expert feedback to determine the usefulness of the alignments. We propose a learning approach that uses existing biologically significant alignments to learn parameters for intelligently processing sub-optimal Smith-Waterman alignments. Our algorithm runs in O(n2) time and can discover biologically significant alignments without requiring expert feedback to produce meaningful results.