Hidden in your genetic code, if it's reversed, results in the phenotype of the conflictor. This can be observed in pairs of monozygotic twins (who are actually clones) that are always either identicals or conflictors. In other words, conflictors are genetic identicals (but phenotypical opposites).

Mew - SEI
Mewtwo - LIE

I am not knowledgeable about the mechanism which results in one or the other.