S-phase (synthesis phase) is the part of the cell cycle in which DNA is replicated, occurring between G₁ phase and G₂ phase. Precise and accurate DNA replication is necessary to prevent genetic abnormalities which often lead to cell death or disease. Due to the importance, the regulatory pathways that govern this event in eukaryotes are highly conserved. This conservation makes the study of S-phase in model organisms such as Xenopus laevis embryos and budding yeast relevant to higher organisms.