The cell cycle: prepare, divide the nucleus, divide the cell
導入済み| English | 意味 |
|---|---|
| mitosis/maɪˈtəʊsɪs/ | 有糸分裂 |
| cell cycle/sel ˈsaɪkl/ | 細胞周期 |
What would explain this observation?
- A cell must copy genetic material before distributing it to two daughter cells. Growth alone cannot provide each daughter with a complete genetic set.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Before division, a cell grows and increases its sub-cellular structures, including ribosomes and mitochondria. Its DNA replicates to give two copies of each chromosome. During mitosis 有丝分裂, one set is pulled to each end and the nucleus divides. Finally, cytoplasm and cell membranes divide, forming two genetically identical daughter cells under the normal model.
- mitosis: Nuclear division distributing chromosome copies into genetically identical nuclei; cell cycle 细胞周期: The sequence of cell growth, DNA copying and division.
Which event must occur before chromosome copies are separated?
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Copies can be separated only after they exist: DNA replication comes first, then mitosis distributes the copies. Losing all chromosomes would kill the cell, and gametes are made by meiosis, not mitosis.
Match each technical term to its precise meaning.
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Use three overall stages: growth and DNA copying, mitosis, then cell division. AQA does not require the named phases within mitosis at this point. Mitosis supports growth and development in multicellular organisms and repair or replacement in mature animals; it does not produce genetically varied haploid gametes.
- Observe school-prepared dividing-tissue images or use chromosome-copy models. Trace one copied chromosome through nuclear division and into each daughter. Identify whether an example describes more cells, specialized cell functions or gamete formation before naming its process.
Which two habits make the investigation or model in this case more defensible?
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: a model cell has eight chromosomes before DNA replication. The copied genetic material is shared through mitosis so each daughter normally has eight chromosomes. If one starting cell completes four successive ideal division rounds with no loss, cell number is 2⁴=16. Each cell still has the model chromosome number eight.
Three model starting cells each complete three division rounds. Calculate the final number. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Three model starting cells each complete three division rounds. Calculate the final number.
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
The result is 24 cells. Known: 3 starting cells; three division rounds each. Each starting cell gives 2^3 = 8 cells, so the final number = 3 x 8 = 24 cells.
Check the conclusion and its limits
- Mitosis divides a nucleus; the complete cell cycle includes preparation and division of the cell. “Identical” concerns the normal copied genetic information in this model, not a claim that every cell is physically the same size at every moment.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Mitosis normally halves the chromosome number of each daughter cell. This claim is false: Mitosis conserves the chromosome number: after DNA replication the copies are shared so each daughter normally gets the full set. Halving belongs to meiosis.
The cell cycle: prepare, divide the nucleus, divide the cell: Use three overall stages: growth and DNA copying, mitosis, then cell division. AQA does not require the named phases within mitosis at this point. Mitosis supports growth and development in multicellular organisms and repair or replacement in mature animals; it does not produce genetically varied haploid gametes.
Mitosis normally halves the chromosome number of each daughter cell.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
Mitosis conserves the chromosome number: after DNA replication the copies are shared so each daughter normally gets the full set. Halving belongs to meiosis.
Nuclear division distributing chromosome copies into genetically identical nuclei: write the technical term.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
mitosis means Nuclear division distributing chromosome copies into genetically identical nuclei.