Infographic: How Prime Editing Works

Prime editing is one of the most promising forms of genome editing because it uses only single-stranded DNA breaks.

Written byIda Emilie Steinmark, PhD
| 6 min read

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The prime editing machinery comprises a prime editing guide RNA (pegRNA) and a Cas9 nickase enzyme fused to a reverse transcriptase.

The prime editing machinery comprises a prime editing guide RNA (pegRNA) and a Cas9 nickase enzyme fused to a reverse transcriptase.
(Left) The pegRNA binds to a matching sequence on the target DNA strand.(Right) The Cas9 nickase cuts the unbound complementary strand, creating a flap.
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The pegRNA binds to a matching sequence on the target DNA strand.

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The Cas9 nickase cuts the unbound complementary strand, creating a flap.

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The dangling DNA flap binds to a matching sequence on the other end of the pegRNA.

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The reverse transcriptase extends the flap by filling in the desired insertion sequence from the template next to the binding site.


The edited flap competes with and displaces the flanking nucleotide sequence (right), which is ultimately removed by the cell. The opposite strand is nicked and repaired to match
the newly edited flap, completing the edit.
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The edited flap competes with and displaces the flanking nucleotide sequence (right), which is ultimately removed by the cell.

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The opposite strand is nicked and repaired to match the newly edited flap, completing the edit.

modified from © istock.com, ttsz; designed by erin lemieux
  1. Anzalone AV, et al. Search-and-replace genome editing without double-strand breaks or donor DNA. Nature. 2019;576(7785):149-157.

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Meet the Author

  • Black and white portrait of Ida Emilie Steinmark, PhD

    Emilie joined the Scientist as an assistant editor in 2023 after writing for publications such as the Guardian, Scientific American, and STAT. She has a degree in chemistry and a PhD in biophysics, but she enjoys writing about everything from ancient DNA to organoids. She lives in Brooklyn, where she can often be found searching for songbirds with her binoculars. 

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