Ayesha counts 250 cells in a root tip. She finds 20 in prophase, 6 in metaphase, 3 in anaphase and…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Ayesha counts cells in a root tip. She finds in prophase, in metaphase, in anaphase and in telophase. The rest are in interphase. The cycle of these cells takes h, and the cells do not divide in step.
- How many cells are in mitosis?
- What is the mitotic index?
- How long does the whole of M phase last?
- How long does prophase last, in minutes?
Need a reminder? The key ideaShow
Count the centromeres for the chromosomes and the DNA molecules for the chromatids. The mitotic index is the cells in mitosis divided by all the cells, times . The time of a phase is the share of the cells in it times the length of the cycle. One cell gives cells in cycles, and divisions take place in going from to cells.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. cells; prophase , metaphase , anaphase , telophase ; cycle h.
Plan. Add the counts. Then use the share of cells as the share of time.
Step 1. Cells in mitosis. .
Step 2. Mitotic index. .
Step 3. M phase. .
Step 4. Prophase. .
Answer: cells; ; h; min.
Check. Prophase has the most cells, so it should take the longest of the four stages. Its min is longer than the h 4 average of min.
Watch out. The method is valid only when the cells divide at random. A culture whose cells are all in step would give a false answer.
Discussion (0)
Log in to join the discussion.
Loading…