Survival of organisms is highly depended on the stability of mitochondrial and genomic DNA, maintained by DNA repair proteins. Deficiencies in DNA repair genes or impairment in expression level can cause increased risk of cancer as well as aging related diseases. DNA repair pathways; namely base excision repair (BER), mismatch repair (MMR), nucleotide excision repair (NER) and non-homologous end-joining (NHEJ) are strongly associated with the aging process and aging related diseases. Deficiencies in DNA repair genes can lead to accumulation of DNA lesions, especially after exposure to DNA damaging reagents. Unrepaired DNA is postulated to be an underlying cause of neurodegenerative diseases, such as Alzheimer’s disease (AD) and Huntington’s disease (HD).