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Meiosis Stages Explorer

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About This MicroSim

This interactive diagram shows all stages of meiosis in two rows: Meiosis I (top row) and Meiosis II (bottom row). Sixteen callout markers highlight key structures and concepts across all 9 stages, from interphase through the production of four genetically unique haploid cells.

Use Explore mode to hover over any marker or label and read detailed descriptions including AP Exam Tips.

Switch to Quiz mode to test your ability to identify meiotic structures and concepts.

Structures and Concepts by Stage

Meiosis I (Reductional Division)

Interphase

  1. Unreplicated chromosomes (2n) — Diffuse chromatin; DNA replicates during S phase

Prophase I

  1. Synapsis and tetrad formation — Homologs pair up to form bivalents
  2. Crossing over (chiasmata) — Non-sister chromatids exchange segments

Metaphase I

  1. Bivalents at metaphase plate — Paired homologs align at the cell equator
  2. Independent assortment — Random orientation of each bivalent

Anaphase I

  1. Homolog separation — Homologous chromosomes move to opposite poles
  2. Sister chromatids still joined — Centromeric cohesin protected by shugoshin

Telophase I / Cytokinesis I

  1. Two haploid cells (n) — Each with n chromosomes, still as sister chromatids

Meiosis II (Equational Division)

Prophase II

  1. New spindle formation — Spindle assembles in each haploid cell

Metaphase II

  1. Individual chromatid alignment — Chromosomes align at metaphase plate (no bivalents)

Anaphase II

  1. Sister chromatid separation — Centromeric cohesin cleaved; V-shaped chromatids separate

Telophase II / Cytokinesis II

  1. Four unique haploid cells — Genetically distinct due to crossing over and independent assortment
  2. Recombinant chromosomes — Mixed maternal/paternal segments from crossing over

Conceptual Markers

  1. Reductional division (Meiosis I) — Halves chromosome number (2n → n)
  2. Equational division (Meiosis II) — Separates sister chromatids (n → n)
  3. Nondisjunction risk — Failure of chromosomes to separate causes aneuploidy

How to Use

  1. Explore mode (default): Hover over any numbered marker or label to see a description and AP Exam Tip
  2. Quiz mode: Click the Quiz button — labels are hidden and you must click the correct marker for each prompted structure
  3. Edit mode: Open main.html?edit=true in a browser to drag markers and calibrate positions

Lesson Plan

Grade Level

9-12 (AP Biology)

Duration

15-20 minutes

Prerequisites

  • Understanding of mitosis and the cell cycle
  • Chromosome structure (homologs, sister chromatids, centromeres)
  • Diploid vs. haploid concepts

Activities

  1. Exploration (7 min): Students explore all 16 markers, comparing Meiosis I and Meiosis II stages side by side
  2. Comparison (5 min): Students identify the key differences between anaphase I (homologs separate, X-shaped) and anaphase II (sister chromatids separate, V-shaped)
  3. Quiz Assessment (5 min): Students complete Quiz mode, identifying all structures and concepts

Assessment

  • Students should explain why meiosis I is called the "reductional" division
  • Students should identify what separates in anaphase I vs. anaphase II
  • Students should describe how crossing over and independent assortment generate genetic variation
  • Students should explain what nondisjunction is and name a condition it causes

References

  1. Meiosis - Wikipedia
  2. Phases of Meiosis - Khan Academy
  3. Campbell Biology, 12th Edition — Chapter 13: Meiosis and Sexual Life Cycles