sentences:  At the gene level, the mutations were found to cause primarily single-base substitution mutations, which suggests that the role of hMSH6 is primarily for correcting single-base substitution mutations and to a lesser extent single base insertion/deletion mutations.Mutations in the hMSH6 gene cause the protein to be nonfunctional or only partially active, thus reducing its ability to repair mistakes in DNA.The loss of MSH6 function results in instability at mononucleotide repeats.