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  1. 1-biological-molecules

    1-1-biological-molecules-carbohydrates
    11 主题
  2. 1-2-biological-molecules-lipids
    3 主题
  3. 1-3-biological-molecules-proteins
    5 主题
  4. 1-4-proteins-enzymes
    12 主题
  5. 1-5-nucleic-acids-structure-and-dna-replication
    8 主题
  6. 1-6-atp-water-and-inorganic-ions
    4 主题
  7. 2-cell-structure
    2-1-cell-structure
    7 主题
  8. 2-2-the-microscope-in-cell-studies
    4 主题
  9. 2-3-cell-division-in-eukaryotic-and-prokaryotic-cells
    8 主题
  10. 2-4-cell-membranes-and-transport
    7 主题
  11. 2-5-cell-recognition-and-the-immune-system
    7 主题
  12. 2-6-vaccines-disease-and-monoclonal-antibodies
    6 主题
  13. 3-exchange-and-transport
    3-1-adaptations-for-gas-exchange
    6 主题
  14. 3-2-human-gas-exchange
    10 主题
  15. 3-3-digestion-and-absorption
    5 主题
  16. 3-4-mass-transport-in-animals
    6 主题
  17. 3-5-the-circulatory-system-in-animals
    8 主题
  18. 3-6-mass-transport-in-plants
    6 主题
  19. 4-genetics-variation-and-interdependence
    4-1-dna-genes-and-chromosomes
    7 主题
  20. 4-2-dna-and-protein-synthesis
    6 主题
  21. 4-3-genetic-diversity-mutations-and-meiosis
    7 主题
  22. 4-4-genetic-diversity-and-adaptation
    6 主题
  23. 4-5-species-and-taxonomy
    4 主题
  24. 4-6-biodiversity
    9 主题
  25. 5-energy-transfers-in-and-between-organisms-a-level-only
    5-1-photosynthesis-a-level-only
    5 主题
  26. 5-2-respiration-a-level-only
    7 主题
  27. 5-3-energy-and-ecosystems-a-level-only
    9 主题
  28. 5-4-nutrient-cycles-a-level-only
    4 主题
  29. 6-organisms-respond-to-changes-in-their-environments-a-level-only
    6-1-response-to-stimuli-a-level-only
    12 主题
  30. 6-2-nervous-coordination-a-level-only
    10 主题
  31. 6-3-skeletal-muscles-a-level-only
    6 主题
  32. 6-4-homeostasis-a-level-only
    11 主题
  33. 7-genetics-populations-evolution-and-ecosystems-a-level-only
    7-1-inheritance-a-level-only
    6 主题
  34. 7-2-populations-a-level-only
    3 主题
  35. 7-3-evolution-a-level-only
    5 主题
  36. 7-4-populations-in-ecosystems-a-level-only
    7 主题
  37. 8-the-control-of-gene-expression-a-level-only
    8-1-genetic-mutations-a-level-only
    2 主题
  38. 8-2-regulation-of-gene-expression-a-level-only
    11 主题
  39. 8-3-using-genome-projects-a-level-only
    4 主题
  40. 8-4-gene-technologies-a-level-only
    13 主题
  41. exam-guidance-and-skills
    essay-guidance
    3 主题
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Looking at meiosis under a microscope

  • Cells undergoing meiosis can be observed and photographed using specialised microscopes

  • The different stages of meiosis have distinctive characteristics, meaning they can be identified from photomicrographs or diagrams

Meiosis I or meiosis II

  • Homologous chromosomes pair up side by side in meiosis I only

  • This means if there are pairs of chromosomes in a diagram or photomicrograph meiosis I must be occurring

  • The number of cells formed can help distinguish between meiosis I and II

    • If two new cells are formed, it is meiosis I, but if four new cells are formed, it is meiosis II

  • During meiosis II, single chromosomes may be observed

Stage of meiosis

What may be observed

Prophase I

Homologous pairs of chromosomes are visible

Metaphase I

Homologous pairs are lined up side by side along the equator of spindle

Anaphase I

Whole chromosomes are being pulled to opposite poles with centromeres intact

Telophase I

There are two groups of condensed chromosomes around which nuclear membranes are forming

Prophase II

Single whole chromosomes are visible

Metaphase II

Single whole chromosomes are lined up along the equator of the spindle in a single file

Anaphase II

Centromeres divide, and chromatids are pulled to opposite poles

Telophase II

Nuclei are forming around the 4 groups of condensed chromosomes

Examples of cells in meiosis

  • Metaphase I vs metaphase II

A micrograph illustration of a cell in metaphase one of meiosis,
Metaphase I
Illustration of mitosis, showing a cell during meiosis two
Metaphase II

  • Telophase I vs telophase II

Cell during telophase one
Telophase I
Four haploid cells seen under a microscope during telophase two
Telophase II

Examiner Tips and Tricks

You do not need to know the specific stages of meiosis, but you do need to be able to recognise where meiosis occurs when given information about an unfamiliar life cycle, and you should be given opportunities to examine meiosis in prepared slides of suitable plant or animal tissue.