abnormal mitotic G1/S phase transition mitotic G1/S phase transition at small cell size small cell size at G1/S transition of mitotic cell cycle mitotic G1/S phase transition at small cell size during vegetative growth G1/S phase transition at small cell size during mitotic cell cycle FYPO:0006909 A G1/S delay may indicate that a checkpoint, such as the cell size checkpoint or the G1/S DNA damage checkpoint, is activated. Checkpoint activation can be tested using checkpoint kinase mutants. mitotic G1/S phase transition at abnormally small cell size midori 2019-06-10T15:02:50Z A cell cycle phenotype in which the G1/S transition of the mitotic cell cycle occurs at a smaller cell size than normal after the cell has been arrested in G1 phase due to nitrogen starvation. The cell remains arrested in G1.