These include the major DNA mismatch repair (MMR) genes MLH1 and MSH2 causing Lynch syndrome (LS), the adenomatous polyposis coli (APC) gene prompting familial adenomatous polyposis (FAP), and the BRCA1 and BRCA2 genes that are strongly associated with hereditary breast and ovarian cancer syndromes [21]. Here, APC is linked to Leigh syndrome.