Databases and Comparisons - CMB Education - Karolinska Institutet

PAMThe most important improvement achieved over theunitary matrix was based on evolutionary distances.Margaret O. Dayhoff pioneered this approach in the1970's.– An extensive study of the frequencies in which aminoacids substitute for each other during evolution.– The studies involved carefully aligning all of the proteinsin several families of proteins and then constructingphylogenetic trees for each family.– This lead to a table of relative frequencies with whichamino acids replace each other over an evolutionaryperiod. This table and the relative frequency of occurrenceof amino acids in the proteins studied were combined incomputing the PAM family of scoring matrices.Linköping University & Karolinska Institutet 44