The stages of cell division don't take equal time
- The idea
- Predict
- See it
- Why
- Check
The idea
“Each stage of mitosis or the cell cycle takes about the same time.”
Textbooks draw each stage as one picture of the same size. That makes it easy to picture each stage getting an equal slice of time.
The short version
The mistake: Each stage of mitosis or the cell cycle takes about the same time.
What's actually true: Stages differ a lot in length, and the share of cells caught in a stage shows its share of the time.
- Root tip cells divide on their own schedules. A squash freezes each one at a random moment, so a long stage catches more cells.
- A stage's share of the cells estimates its share of the time. Anaphase holds 18 of 200 cells, 9 percent, so it lasts about 7 of the 80 minutes.
- The same holds for the whole cycle. Interphase holds most cells in a sample because it takes up most of the cycle.
On the exam: A stage's share of the cells is its share of the time. Never split the time evenly.