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Biology · Grades 9–12

Cell cycle and mitosis

Separate DNA replication from chromosome separation.

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Learn the idea

Cycle

The cell cycle includes growth, DNA replication and division-related stages.

Replication

DNA is copied before mitosis; mitosis itself organizes and separates the copied chromosomes.

Mitosis

In a typical stable diploid model, mitosis preserves chromosome number in daughter nuclei.

Control

Division is regulated; an unregulated increase in cells is not the normal purpose of every cell type.

Worked examples

When is DNA copied for a typical mitotic division?

Replication precedes mitotic chromosome separation.

Before mitosis, during S phase.

A diploid parent cell has 8 chromosomes. In the standard mitosis model, how many chromosomes does each daughter nucleus receive?

Mitosis preserves the chromosome number in this model.

8

Check your understanding

  1. What separates during mitotic anaphase?

    1. Entire species.
    2. Sister chromatids.
    3. Only all cell membranes.

  2. Starting with one cell, two complete rounds of division produce how many cells if none die?

  3. Why is DNA replication not the same event as cell division?

Answers and marking notes

Answers and marking notes
  1. Sister chromatids.

    Chromatids separate and move toward opposite poles.

  2. 4

    Each cell divides into two: one cell becomes two, then those two become four cells.

  3. Replication copies genetic material; division distributes material into daughter cells.

    Distinguish copying from physical separation.

Further reading and review references

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Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.