OCR · A-Level · Biology

    Course version: H420 · Version from Sept 2025

    (g) the main stages of meiosis

    Full specification wording

    Cell division, cell diversity and cellular organisation: (g) the main stages of meiosis

    Meiosis has two divisions after one round of DNA replication.

    Checked against the OCR H420 specification (opens in a new tab) on .

    • Point 7 of 13
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    Meiosis has two divisions after one round of DNA replication. In prophase I homologous chromosomes pair as bivalents and crossing over occurs at chiasmata. In metaphase I bivalents line up on the equator and independent assortment occurs. In anaphase I homologous chromosomes separate to opposite poles. Telophase I and cytokinesis give two haploid cells. In prophase II the nuclear envelope breaks down; in metaphase II chromosomes line up singly on the equator; in anaphase II sister chromatids separate; telophase II and cytokinesis give four haploid cells. Each product is genetically different.

    What earns the marks

    • Prophase I: homologous chromosomes pair as bivalents and crossing over occurs at chiasmata.
    • Metaphase I: bivalents line up on the equator and independent assortment of homologues occurs.
    • Anaphase I: homologous chromosomes separate to opposite poles; telophase I and cytokinesis give two haploid cells.
    • Metaphase II: chromosomes line up singly on the equator; anaphase II separates sister chromatids.
    • Telophase II and cytokinesis produce four haploid cells that are genetically different.

    Common mistakes and how to put them right

    • Confusing the two divisions.

      Put it right: Is that homologues separate in anaphase I and sister chromatids separate in anaphase II.

    • Placing crossing over in the wrong stage.

      Put it right: Is that it occurs in prophase I at chiasmata.

    • Saying four identical cells result.

      Put it right: Is that four haploid cells form and they are genetically different.

    Exam tips

    • Use the division number (I or II) with each stage name so the sequence is unambiguous.
    • State what separates at each anaphase: homologues in anaphase I, sister chromatids in anaphase II.
    • Track the chromosome number through the stages to show where the halving happens.

    Try the lesson

    The start of the Cell division, cell diversity and cellular organisation: (g) the main stages of meiosis lesson, made from checked teaching notes for this specification point.

    Have a go first

    During which stage of meiosis do homologous chromosomes separate and move to opposite poles of the cell?

    Listen

    Meiosis has two divisions after one round of DNA replication. In prophase I homologous chromosomes pair as bivalents and crossing over occurs at chiasmata. In metaphase I bivalents line up on the equator and independent assortment occurs. In anaphase I homologous chromosomes separate to opposite poles. Telophase I and cytokinesis give two haploid cells. In prophase II the nuclear envelope breaks down; in metaphase II chromosomes line up singly on the equator; in anaphase II sister chromatids separate; telophase II and cytokinesis give four haploid cells. Each product is genetically different. A strong answer earns marks for these points. Prophase I: homologous chromosomes pair as bivalents and crossing over occurs at chiasmata. Metaphase I: bivalents line up on the equator and independent assortment of homologues occurs. Anaphase I: homologous chromosomes separate to opposite poles; telophase I and cytokinesis give two haploid cells. Metaphase II: chromosomes line up singly on the equator; anaphase II separates sister chromatids. A common slip: Confusing the two divisions. Instead, is that homologues separate in anaphase I and sister chromatids separate in anaphase II. Exam tip: Use the division number (I or II) with each stage name so the sequence is unambiguous.

    See it

    A vertical flowchart of eight stages. Prophase I leads to Metaphase I: in Prophase I homologous chromosomes pair as bivalents and crossing over occurs at chiasmata; in Metaphase I bivalents line up on the equator and independent assortment occurs. Metaphase I leads to Anaphase I, where homologous chromosomes separate to opposite poles. Anaphase I leads to Telophase I and cytokinesis, giving two haploid cells. This leads to Prophase II, where the nuclear envelope breaks down. Prophase II leads to Metaphase II, where chromosomes line up singly on the equator. Metaphase II leads to Anaphase II, where sister chromatids separate. Anaphase II leads to Telophase II and cytokinesis, producing four haploid cells that are genetically different.
    The sequence of the main stages of meiosis I and meiosis II, showing what happens at each stage and where the halving occurs.

    Put it in order

    Put these steps in the order they happen.

    1. 1. Prophase II: nuclear envelope breaks down
    2. 2. Telophase II and cytokinesis: four haploid cells, genetically different
    3. 3. Metaphase II: chromosomes line up singly on the equator
    4. 4. Prophase I: homologous chromosomes pair as bivalents; crossing over at chiasmata
    5. 5. Metaphase I: bivalents line up on the equator; independent assortment
    6. 6. Anaphase II: sister chromatids separate
    7. 7. Anaphase I: homologous chromosomes separate to opposite poles
    8. 8. Telophase I and cytokinesis: two haploid cells

    Key words

    Say what each word means before you turn the card.

    Two divisions after one replication

    Try answering aloud or in your head before turning the card.

    Bivalents and chiasmata

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    Independent assortment

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    Separation of homologues then chromatids

    Try answering aloud or in your head before turning the card.

    See every definition
    Two divisions after one replication
    Meiosis has two divisions after one round of DNA replication, giving four haploid cells.
    Bivalents and chiasmata
    In prophase I homologous chromosomes pair as bivalents and crossing over occurs at chiasmata.
    Independent assortment
    In metaphase I bivalents line up on the equator and independent assortment of homologues occurs.
    Separation of homologues then chromatids
    Homologous chromosomes separate in anaphase I and sister chromatids separate in anaphase II.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A vertical flowchart of eight stages. Prophase I leads to Metaphase I: in Prophase I homologous chromosomes pair as bivalents and crossing over occurs at chiasmata; in Metaphase I bivalents line up on the equator and independent assortment occurs. Metaphase I leads to Anaphase I, where homologous chromosomes separate to opposite poles. Anaphase I leads to Telophase I and cytokinesis, giving two haploid cells. This leads to Prophase II, where the nuclear envelope breaks down. Prophase II leads to Metaphase II, where chromosomes line up singly on the equator. Metaphase II leads to Anaphase II, where sister chromatids separate. Anaphase II leads to Telophase II and cytokinesis, producing four haploid cells that are genetically different.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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