Human cells grown in culture divide about once every 24 h…
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Human cells grown in culture divide about once every . Yeast can go through its cell cycle in about . Take every cell to divide on time.
- A culture starts with human cells. How many cells are there after ?
- A culture starts with one yeast cell. How many cells are there after ?
- One cell and all its descendants divide by mitosis until there are cells. How many rounds of division does this take, and how many cell divisions take place in all?
The worked solution
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(a) Human cells. cycles, so the number doubles times: cells.
(b) Yeast. , which is cycles: cells.
(c) Rounds and divisions. , so rounds are needed. Every single division turns one cell into two, adding one cell. Going from cell to cells needs divisions ().
Answer: (a) cells. (b) cells. (c) rounds and divisions.
Check. In (c), the divisions round by round are and ; their sum is , one less than the final number of cells.
Watch out. "How many divisions" and "how many rounds" are different questions. A round doubles every cell at once; a division is one cell splitting into two.
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