# How does the Illumina/Nextera tagmentation enzyme make sure that both p5 and p7 adapters are added?

The tagmentation enzyme used by Illumina is pre-loaded with both read 1 and read 2 DNA oligo tags in a complex DNA-enzyme structure which makes sure that sequences are added to both ends of the DNA fragmentation site. This is the tagmentation transposome which is used in both bead-linked and free-solution tagmentation enzymes. Subsequent protocol steps are optimized to produce library fragments with one p5 side adapter and one p7 side adapter to allow for sequencing compatibility.

**The following kits use a free-solution transposome:**

* Nextera XT
* Illumina Tagment DNA Enzyme and Buffer Kits

  ![](https://761066130-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FGM9W2DuBTgEXv1ClCm8H%2Fuploads%2Fgit-blob-d2da21692ca6f3bb748e89c2e867de559f053092%2Fimage1.png?alt=media)

**The following kits use a bead-linked transposome (the following use different bead-linked versions):**

* Illumina DNA Prep
* Illumina DNA Prep with Enrichment
* Illumina DNA PCR-Free
* Illumina RNA Prep with Enrichment (tagments double stranded cDNA)

  ![](https://761066130-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FGM9W2DuBTgEXv1ClCm8H%2Fuploads%2Fgit-blob-f66fea65ec45c342971106df17b8d9c671fca090%2Fimage2.png?alt=media)

The [bead-linked transposome](https://www.illumina.com/techniques/sequencing/ngs-library-prep/tagmentation.html) allows for greater flexibly of input DNA amounts so that a wide range of DNA inputs can be used to achieve a consistent library size.

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