Name the phase of the cell cycle that fits each clue…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Name the phase of the cell cycle that fits each clue.
- A cell has C of DNA and chromosomes. It is growing and making the proteins needed for division.
- A nerve cell has C of DNA, is metabolically active and never divides.
- The DNA content of a cell is somewhere between C and C and is rising.
- A cell has just been formed. It has C of DNA, it grows, and it has not started to copy its DNA.
- The centrosome of an animal cell is copied in this phase.
Need a reminder? The key ideaShow
A human cell in culture takes about 24 hours to go round the cycle: G1 about 11 h, S about 8 h, G2 about 4 h and M about 1 h. Interphase is G1, S and G2. S phase raises the DNA from 2C to 4C and gives every chromosome a second chromatid. The number of chromosomes stays 2n.
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.
Step 1. (a) G2. The DNA is already copied (C), and the cell prepares for mitosis.
Step 2. (b) G0, the quiescent stage. The cell is active, but it has left the cycle.
Step 3. (c) S phase. The DNA is being copied.
Step 4. (d) G1.
Step 5. (e) S phase. The centrosome is copied together with the DNA.
Answer: (a) G2; (b) G0; (c) S; (d) G1; (e) S.
Watch out. A cell in G0 and a cell in G1 both have C of DNA. Only the G1 cell is still in the cycle.
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