In the absence of POT1 the telomeric C-strand is resected and RPA and recombination proteins associate with the overhang. RAD51-coated overhangs invade telomeric DNA of adjacent chromosome ends and the invading 3'end is extended by DNA polymerases. Accumulation of R-loops at telomeres facilitates strand invasion. In case of proper dissolution of the HR intermediates, telomeres are elongated and fragility is due to abnormal chromatin condensation after HDR. Defective dissolution of the HR intermediates leads to accumulation of branched DNA structures. Incomplete fill-in synthesis leads to accumulation of G-rich single stranded DNA. 