Meiosis follows a defined sequence of events, starting with DNA synthesis (S-phase), where chromosomes are replicated to form identical sister chromatids, linked by cohesin rings. During meiosis, however, it is necessary to link homologous chromosomes (homologs). The cell makes programmed double strand breaks (see below) in its own genome, which are then repaired via homologous recombination. In meiosis, the repair of these DNA breaks is directed to the homologs. Some breaks are repaired as crossovers which link the homologs together. Once linked, the homologous chromosomes are separated (end of meiosis I), and the sisters are subsequently separated (meiosis II).