Oncogene — dominant gain-of-function mutations promote cell transformation Tumor suppressor gene — recessive, loss-of-function mutations promote cell transformation Images removed due to copyright reasons. growth checks (DNA synthesis) S G 1 G 0 G 2 Extracellular control signals Intracellular quality control Daughter cells M (Mitosis) Figure by MIT OCW. Cell cycle in S. cerevisiae Mother cell Growth Spindle pole body duplication Spindle formation Chromosome segregation; Cytokinesis M G 1 G 2 S Daughter cell START Bud emergence DNA replication Nuclear migration nuclear division Figure by MIT OCW. A Genetic Screen for Cell Cycle Mutants Figure by MIT OCW.