In a knock-out model of MutS homolog 6 (MSH6), a key MMR gene, 1663 indels occurred on the non-template strand polyT tracts, whereas 1165 indels occurred on template polyT tracts, corresponding to a 16.9% corrected increase in frequency on the non-template strand (binomial test, p value < e − 6), a similar magnitude to that observed in cancers. The gene discussed is MSH6; the disease is cancer.