An animal cell in G1 phase has one centrosome with its 2 centrioles…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
An animal cell in G1 phase has one centrosome with its centrioles.
- How many centrioles does the cell have in G2 phase?
- How many microtubules make up all the centrioles of the cell in G2 phase? Count a triplet as three microtubules.
- The cell divides by mitosis, and its daughters and their daughters divide too, three rounds in all. How many cells are there at the end, and how many centrioles do they have together when all of them are in G1 phase?
The worked solution
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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.
(a) After S phase. The centrosome duplicates during S phase, so a G2 cell has two centrosomes, each with two centrioles: centrioles.
(b) Microtubules. Each centriole has nine evenly spaced peripheral fibrils, and each fibril is a triplet, so it has microtubules. For centrioles: microtubules.
(c) Three rounds of mitosis. Each round doubles the number of cells: cells. At each division the two centrosomes go to opposite poles, so every daughter cell starts G1 with one centrosome of two centrioles. Together: centrioles.
Answer: (a) centrioles. (b) microtubules. (c) cells, with centrioles in all.
Check. Follow one round: a G1 cell with centrioles has in G2 and gives two daughters with each. So the number of centrioles per G1 cell stays in every generation, and the total is times the number of cells.
Watch out. A centrosome is the organelle; the centrioles are the two cylinders inside it. Plant cells of almost all kinds have no centrioles, so this count is for animal cells.
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