SIFT Score: A probability value based on sequence homology and conservation. This value serves as a prediction for whether the mutation will be deleterious or not. Those values colored red are predicted deleterious, those in green are tolerated.
SIFT, http://blocks.fhcrc.org/sift/SIFT.html, Sorting Intolerant from Tolerant, is a sequence homology-based tool which predicts whether an amino acid substitution in a protein will have a pheontypic effect. These predictions are based on conservation in a multiple sequence alignment using a position specific scoring matrix.
SIFT predictions for all nonsynonymous SNPs and mutations have been found using a local copy of the software. Scores given by this run and those provided by the online server available on the SIFT wesite may differ. This is due to differences in the source protein sequences used to perform the alignments. Some nonsynonymous SNPs may also result in a 1.00 TOLERATED score, also due to the differences in the source protein sequences.
The SIFT software is generously provided by Pauline Ng, Ph. D.
For more information see the SIFT website, http://blocks.fhcrc.org/sift/SIFT.html, or
SIFT: Predicting deleterious substitutions, Ng, P.C. and Henikoff, S. (2001) Genome Research 11: 863-874