The cell cycle: prepare, divide the nucleus, divide the cell
| English | 中文 | Pinyin |
|---|---|---|
| mitosis/maɪˈtəʊsɪs/ | 有丝分裂 | yǒu sī fēn liè |
| cell cycle/sel ˈsaɪkl/ | 细胞周期 | xì bāo zhōu qī |
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?
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.
Match each technical term to its precise meaning.
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?
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.
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.
The result is 24 cells. 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.
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 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.
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.
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.
Nuclear division distributing chromosome copies into genetically identical nuclei: write the technical term.
mitosis means Nuclear division distributing chromosome copies into genetically identical nuclei.