This lecture explores the titration of maternal factors, particularly histones H3 and H4, during the Maternal-to-Zygotic Transition (MZT). It delves into the mechanisms of transcription, DNA ratios, and the impact of H3 depletion on gene expression. The importance of Zelda, cyclin B3, and S phase extension through checkpoint engagement are also discussed, along with the gradual prolongation of S phase and the role of zygotic string transcription in creating mitotic domains.