During Cancer Genetics from 1977 to 1983, the field shifts toward a molecular understanding of cancer, treating oncogenesis as the consequence of specific genetic alterations. It becomes evident that a single nucleotide change can convert a normal gene into an oncogene, establishing a causal mechanism for carcinogenesis and foreshadowing later Ras family discoveries. The era emphasizes cloning, sequencing, and cross-cancer comparisons to map mutational processes, while recognizing a two-step, irreversible mutational pathway from stem cells to cancer that integrates spontaneous, hereditary, and environmental factors into a unifying model. Contemporary methods illuminate how precise genetic changes drive malignant transformation, and underscore the centrality of mutational events in cancer risk and progression.