# Can DADA2 be carried on pre-joined reads

**URL:** https://forum.qiime2.org/t/can-dada2-be-carried-on-pre-joined-reads/7269
**Category:** User Support
**Tags:** dada2
**Created:** [December 3, 2018, 9:37pm UTC](https://forum.qiime2.org/t/can-dada2-be-carried-on-pre-joined-reads/7269 "2018-12-03T21:37:53Z")
**Posts on this page:** 1
**Showing post:** 2

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### Author: ![Mehrbod\_Estaki](https://forum.qiime2.org/user_avatar/forum.qiime2.org/mehrbod_estaki/32/4001_2.png) [@Mehrbod\_Estaki](https://forum.qiime2.org/u/Mehrbod_Estaki)
#### Post date: [December 4, 2018, 5:24am UTC](https://forum.qiime2.org/t/can-dada2-be-carried-on-pre-joined-reads/7269/2 "2018-12-04T05:24:15Z")

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Hi @sindhu_mohandas,  
No actually, Dada2 will not perform properly if your reads are pre-joined with another tool. The main issue is that this is in conflict with the error-building approach utilized by Dada2. When you join reads you are assigning new quality scores (calculated differently between different tools) in the overlapping region which are not true q-scores which Dada2 uses. So, you want to run raw data without any prior modifications. What you've done is more appropriate for Deblur however, as Deblur uses a static error model and does not rely on quality scores.

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