Substitution mutation. Definition. A type of point mutation in which a single nucleotide is substituted with (or exchanged for) a different nucleotide that may result in an altered sequence of amino acid during translation, which may render the newly synthesized protein ineffective.Supplement.n transversion, purine is substituted with pyrimidine or a pyrimidine with a purine. See also: point mutation. Please contribute to this project, if you have more information about this term feel free to edit this page. This page was last modified on 16 October 2008, at 00:53.This page has been accessed 109,894 times.