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DNA holds instructions
DNA contains the information that a cell uses to build proteins and do its work.
Biology · 25 minutes
What must happen before a cell splits?
A cell contains DNA instructions. If it simply split its contents in half, each new cell would lose instructions. Decide how you think the cell solves this problem.
Keep this question in mindHow can one cell make two cells without losing half its DNA?
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Look at the evidence
These are living cells at different moments.
The image came from a growing onion root. A stain makes DNA dark. Some cells have one broad nucleus. Others have visible chromosome shapes.
One root tipcaught in many moments.Every dark chromosome came from DNA that was copied first.
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Three things to know
The problem is not making two cells. It is making two complete cells.
Follow the DNA. Each new cell needs the same full set of instructions.
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A chromosome is packed DNA
Before division, long DNA molecules coil into compact chromosomes that a microscope can reveal.
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Both new cells need a full set
A useful new cell needs the complete set of chromosomes, not a random half of them.
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Your prediction
How does one cell give both new cells a complete set of DNA?
Pick the order that seems possible. The experiment will make you account for every chromosome.
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