In this study, we investigate the outcomes of the Dbf4 gene knockout on female mice infertility. Dbf4, also known as Dbf4p, was initially identified in Saccharomyces cerevisiae. DBF4 was recognized as a regulatory subunit of the Cdc7p-Dbf4p kinase complex (DDK), which is required for Cdc7 kinase activity and initiation of DNA replication by phosphorylating Mcm2-7 proteins during the cell cycle. After activation with DBF4 binding, DDK phosphorylates the MCM2-7 helicase to fire the replication origin, committing the cell to S-phase transition. Additionally, Dbf4-dependent kinase protein is a major cell cycle regulator of DNA end resection and is required for homologous recombination (HR) activation. Early mammalian embryo development relies on a successful transition in the S-phase of the cell cycle, which is enabled almost entirely by maternal replication factors stored during oocyte development. In the mouse model, immature germinal vesicle (GV) oocytes had high levels of Cdc7 with a lack of kinase activity due to low levels of the regulatory subunit, DBF4. As oocytes mature, DBF4 accumulates, which leads to the activation of Cdc7 kinase. This activation is crucial for initiating DNA replication in zygotes post-fertilization. By using a conditional knockout model, our research demonstrated that cKO of Dbf4 results in embryonic arrest at the one-cell stage, with no significant difference in ovulation rate between control and cKO mice. We assess defects in DNA replication, DNA damage, and chromatin remodeling using Immunofluorescence staining and EdU incorporation assay. These findings highlight Dbf4 as a critical factor in early embryogenesis and infertility.