Summary
DNA replication is an essential process for genome duplication, cell division and ultimately organismal survival that ensures faithful transmission of the genome to progeny. Certain genomic loci represent major obstacles to DNA replication including fragile sites, G-rich tracts and repetitive sequences, such as rDNA and telomeres. Mammalian telomeres have the propensity to adopt complex DNA secondary structures, including telomere-loops and telomeric G-quadruplex, which are believed to play essential roles in telomere maintenance. However, recent work has established that these structures are also a hindrance to DNA replication and might represent a potential source of genome instability, the hallmark of many diseases including cancer.