This course provides an extensive overview of cell cycle control, DNA replication, and the role of genomic instability in cancer development. They detail the phases of the cell cycle (G1, S, G2, M) and the cyclin-dependent kinases (CDKs) that regulate progression through them, highlighting how growth factors and signaling pathways like RTK-Ras-MAP and TGF-$\beta$ influence these processes. A significant portion focuses on the mechanisms leading to genomic instability, such as deficiencies in DNA repair systems (e.g., NER, MMR, DSB repair) and errors during replication, associating these with diseases like cancer and Xeroderma pigmentosum. Finally, the texts explore potential therapeutic strategies that exploit these vulnerabilities in cancer cells, specifically discussing the use of checkpoint kinase inhibitors (ATR, CHK1, WEE1) and the synergistic effects of combining them with inhibitors targeting factors like TLK2 and HDAC8.