In a hospital laboratory in Cairo, a machine measures the DNA of 10000 cells of a culture…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
In a hospital laboratory in Cairo, a machine measures the DNA of cells of a culture. The cells divide at random, and the whole cycle takes h. It finds cells at C, cells with DNA between C and C, and cells at C.
- Which phase does each region show?
- How long does G1 last?
- How long does S phase last?
- How long do G2 and M together last?
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; , and in the three regions; cycle h.
Plan. The share of cells in a region is the share of the cycle for that phase.
Step 1. The phases. The C peak is G1. The cells in between are in S phase. The C peak holds G2 and M.
Step 2. G1. h.
Step 3. S phase. h.
Step 4. G2 and M. h.
Answer: G1, S, G2 and M; h; h; h.
Check. h, the whole cycle.
Watch out. The method assumes that the cells are not dividing in step and that none dies. Flow cytometry cannot tell G2 from M, because both have C.
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