Developmental biology · Research Worlds
How Dolly the sheep was made
Scientists grew a lamb from a grown-up cell. You will move a nucleus, empty an egg, and see why almost every try failed — except one.
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Watch the 90-second visual story ↗What will you explore?
Wilmut et al., 1997
A cell's current identity is not necessarily its permanent identity.
How does it work?
Watch a 90-second cinematic explanation, or explore a story that pauses so you can change its central mechanism. Inspect the source evidence, compare outcomes and resume the narration. This free Lesson Worlds adaptation needs no account or download; younger learners may want help from a parent or teacher.
Inside the cinematic story
Could a cell start over?
Follow one nucleus into an extraordinary experiment.
Two cells. Different roles.
Adult donor cell + enucleated egg
A new environment.
Donor cell fusion · schematic reconstruction
Take control: Which part would you like to inspect? Before fusion · After fusion
The experiment narrows.
277 → 247 → 29 → 29 → 1
Take control: Inspect a reported stage. 277 fused · 247 recovered · 29 developed · 1 live lamb
How did they check?
Nuclear markers · donor / Dolly / recipient
A result with a boundary.
A remarkable result. A precise limitation.
Discuss the evidence
Before starting, explain what you think this claim means: A cell's current identity is not necessarily its permanent identity. After exploring, choose one stage above and describe what its model helps you see. Separate what you observed in the adaptation from what the original researchers measured.
Read the original publication for its methods, evidence and limitations. Ask which part of the explanation the interactive model leaves out, and what additional evidence you would need to test the claim yourself.
Original schematic reconstruction. Aggregate counts follow the adult mammary line; individual embryo trajectories were not observed here. Nuclear markers do not establish whole-genome identity. Rare undifferentiated cells in the donor culture could not be excluded.
Original research
Viable offspring derived from fetal and adult mammalian cells
I. Wilmut, A. E. Schnieke, J. McWhir, A. J. Kind & K. H. S. Campbell · Nature 385, 810–813 (27 February 1997) · 1997
Educational adaptation by Lesson Worlds. Not affiliated with the authors, Nature, Springer Nature or the Roslin Institute. The original publication may have its own access terms.