Complex sentence: As indicated as in the article Carcinogenesis, a deficiency in DNA repair is occasionally due to a mutation in a DNA repair gene, but much more frequently defciencyof a DNA repair genes is due to epigenetic alterations that reduce or silence DNA repair gene expression.
Split into simpler sentences: As indicated as in the article Carcinogenesis, deficient DNA repair is occasionally due to a mutation in a DNA repair gene. However, much more frequently, defciencies of DNA repair are due to epigenetic alterations that reduce or silence DNA repair gene expression.