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Interphase the quiet setup
The cell grows and every DNA molecule is replicated. Each chromosome is secretly two sister chromatids already — it just cannot be seen through the loose chromatin.
BIOLOGY · INTERACTIVE TOOL
Step through every stage of meiosis — from one diploid cell to four genetically different gametes. Click, drag and zoom a living diagram that shows crossing over happening in colour.
UPDATED · 2025Press play to watch the whole sequence, or jump to any stage below the diagram. Click chromosomes, spindle fibers and cell structures to inspect them — drag to pan, scroll or pinch to zoom in on the action.
Click any structure to inspect it · drag to pan · scroll or pinch to zoom
Every colour and shape in the diagram carries meaning. Learn these eight and you can read any meiosis diagram in any textbook.
The homolog inherited from one parent. Every pair in the diagram has exactly one amber member.
The matching homolog from the other parent — same genes, often slightly different versions.
A chromatid patched by crossing over — its tip came from the partner homolog. Recombination in a single glance.
The waist where sister chromatids are pinned together — and where the spindle grabs. It splits only in meiosis II.
Spindle microtubules. The stronger lines are kinetochore fibers that grip chromosomes; the faint ones are the framework.
The nuclear envelope — solid when intact, dashed when it is dissolving (prophase) or rebuilding (telophase).
The metaphase plate — the invisible equator where chromosomes queue before being pulled apart.
Centriole pairs inside each centrosome — the anchor points that become the spindle's two poles.
Division I pulls matching pairs apart and halves the chromosome number. Division II splits the remaining copies. Click any stage to see it live in the diagram above.
The cell grows and every DNA molecule is replicated. Each chromosome is secretly two sister chromatids already — it just cannot be seen through the loose chromatin.
Chromosomes condense, homologs pair into tetrads, and crossing over trades tips between non-sister chromatids while the nuclear envelope dissolves. Prophase I itself has five substages — more than all the other stages combined.
Tetrads line up at the equator, each pair randomly oriented. Which homolog faces which pole is independent for every pair — this is independent assortment, and it shuffles the deck before a single chromosome moves.
Homologs are pulled to opposite poles. Crucially, centromeres stay whole — each chromosome travels as a pair of sister chromatids. The chromosome number is halved at this exact moment.
Nuclear envelopes re-form and the cell pinches in two. The daughters are haploid — one chromosome from every pair — but each chromosome is still doubled, waiting for round two.
No rest, no DNA copying, no interphase II. Chromosomes re-condense and fresh spindles assemble in both cells — usually at right angles to the first, giving meiosis II its classic staggered look.
Single chromosomes — not pairs — align on new equators, sister chromatids facing opposite poles. It looks exactly like mitosis, except each cell only holds half the deck.
Centromeres split at last and sister chromatids become true chromosomes, pulled to opposite ends — the recombinant ones carrying their brand-new tips with them.
Four haploid cells, each genetically unique: two parental types and two carrying chromosomes rebuilt by crossing over. In animals these become sperm or eggs; in plants, spores or gametes.
Meiosis is not just division — it is biology's variation engine. Three mechanisms stack on top of each other, and every one of them is visible in the diagram above.
Fertilisation merges two cells, so each must arrive carrying half the set. Meiosis drops 46 to 23 chromosomes in humans — the zygote ends up with exactly one set from each parent, generation after generation.
Independent assortment: each of the 23 pairs independently decides which homolog goes to which gamete. That is over 8 million possible gametes from one person — before crossing over is even counted.
When any sperm can meet any egg, chromosome combinations exceed 70 trillion — more than every human who has ever lived. And that still ignores crossing over, which rebuilds the chromosomes themselves.
Everything students usually ask about this meiosis diagram — and the stage it happens in.
Press play to run the whole sequence automatically, or tap any stage chip to jump straight there. Click any structure — chromosomes, spindle fibers, the cleavage furrow — to see what it does, and drag, scroll or pinch to move around and zoom.
Nine in order: interphase, then the four stages of meiosis I (prophase I, metaphase I, anaphase I, telophase I) and the four stages of meiosis II (prophase II, metaphase II, anaphase II, telophase II), ending with the four haploid gametes.
Meiosis I separates homologous chromosome pairs — one of each pair goes to each cell, halving the chromosome number (2n to n). Meiosis II then splits the sister chromatids, much like mitosis, but in cells that already carry only one set.
Crossing over happens in prophase I, when paired homologs trade chromosome tips at points called chiasmata. In the diagram, watch an amber tip appear on a coral chromatid and vice versa — those two-tone chromatids then travel into two of the final gametes.
Amber marks the homolog inherited from one parent and coral the homolog from the other. Two-tone tips are chromatids rebuilt by crossing over. The colors let you follow every chromosome's journey through both divisions.
Mitosis copies once and divides once, producing two genetically identical diploid cells. Meiosis copies once but divides twice, producing four haploid gametes — and it shuffles genes first through crossing over and independent assortment.
No — it is a stylized animal cell with only two chromosome pairs (2n = 4) so every structure stays visible. Human cells have 23 pairs and go through the same nine stages, and egg production divides the cytoplasm unequally, keeping only one large gamete.
Yes. Tapping selects a structure, dragging pans the view, and pinching zooms in or out — the diagram behaves the same with touch as it does with a mouse.
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