The cell cycle of an onion (Allium cepa) root-tip cell is estimated to be 22 h22\text{ h}22 h.
A root-tip squash preparation from an onion plant was observed under a light microscope, and a total of 340340340 cells were counted in the meristematic region. Out of these, 484848 cells were determined to be actively undergoing mitosis.
Explain why the apical meristems of plant roots are frequently selected for preparing squash slides to study mitosis.
Calculate the mean length of time each cell spends undergoing mitosis. Give your answer in minutes, correct to 3 significant figures.
During the eukaryotic cell cycle, progression through different stages is tightly regulated by molecular checkpoints.
Identify the specific phase of interphase during which the cell's genomic DNA content is doubled.
Name the checkpoint that directly monitors cell size and checks that DNA has been completely and accurately replicated before the cell enters mitosis.
If a cell fails to satisfy the requirements of a checkpoint, it may be diverted into a non-dividing phase or undergo programmed cell death. State the name of this non-dividing phase and the term for programmed cell death.
