Sequence search/alignments statistical significance

It is equally important that the evaluation of initial assignment of sequences to a superfamily be made from structural rather than functional criteria. This avoids, for example, trivial but important errors from the use of keyword searches to identify members of a superfamily. It also avoids early bias in determining residues/motifs that are conserved across all members of a superfamily. Multiple alignment and motif analysis provide sensitive methods for structure-based confirmation of sequence similarity. Scoring systems that can be applied to such methods provide verification of the statistical significance associated with the comparisons. 

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