<prompt> Retinoblastoma gene regulates?G1-s phaseG2 to M phaseG0 to G 1 PhaseS-G2 Phase  <response>: harshmohan textbook of pathology 7th edition. active form of RB gene :it blocks cell division by binding to the transcription factor E2F and this inhibits the cell from transcription of cell cycle related gene there by inhibiting the cell cycle at G1. 