In certain cases, such as the Arg300Cys mutation in beta-1,4 N-acetylgalactosaminyltransferase 1 (Uniprot Q00973; leading to spastic paraplegia 26, autosomal recessive) and the Ala241Thr mutation in feline leukemia virus subgroup C receptor-related protein 1 (Uniprot Q9Y5Y0) (leading to posterior column ataxia with retinitis pigmentosa), the impacts of the mutations could only be explained by large changes in ddG of the mutation (>2.5) (Supplementary Figure 14 available online at http://bib.oxfordjournals.org/). This evidence concerns the gene B4GALNT1 and retinitis pigmentosa.