Helicases Maintain Genome Stability In Schizosaccharomyces Pombe A healthy cell needs to accurately duplicate its genome and pass one copy to each of its daughter cells. The DNA double helix is accessed by replication machinery once per cell cycle during S phase and regulated unwinding of this molecule is essential for replication. However, helicase-mediated unwinding can make the DNA vulnerable to damage or breakage. Therefore, the process of unwinding must be carefully regulated.