# Dada2 Parameter problem

**URL:** https://forum.qiime2.org/t/dada2-parameter-problem/17384
**Category:** User Support
**Created:** [November 9, 2020, 11:44am UTC](https://forum.qiime2.org/t/dada2-parameter-problem/17384 "2020-11-09T11:44:12Z")
**Posts on this page:** 5
**Page:** 1

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### Author: ![mohsen\_ej](https://forum.qiime2.org/letter_avatar_proxy/v4/letter/m/b38774/32.png) [@mohsen\_ej](https://forum.qiime2.org/u/mohsen_ej)
#### Post date: [November 9, 2020, 11:44am UTC](https://forum.qiime2.org/t/dada2-parameter-problem/17384/1 "2020-11-09T11:44:12Z")

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Hi  
I need help with dada2 parameters. I'm not sure if I am choosing the best trim&trunc for the data.  
I used 16s V3-V4 and the amplicon size expected is ~460bp.  
these are the primers:  
16S Amplicon PCR Forward Primer = 5'  
TCGTCGGCAGCGTCAGATGTGTATAAGAGACAGCCTACGGGNGGCWGCAG  
16S Amplicon PCR Reverse Primer = 5'  
GTCTCGTGGGCTCGGAGATGTGTATAAGAGACAGGACTACHVGGGTATCTAATCC  
I used cutadapt plugin to remove the primers and adapters and asked you about them in another topic [Remove Primer](https://forum.qiime2.org/t/remove-primer-in-paired-end-demultiplexed-file/17376/2)  
what's your mind about identifying dada2 parameters for this file  
Thank you very much in advance

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### Author: ![andrewsanchez](https://forum.qiime2.org/user_avatar/forum.qiime2.org/andrewsanchez/32/20160_2.png) [@andrewsanchez](https://forum.qiime2.org/u/andrewsanchez)
#### Post date: [November 9, 2020, 6:55pm UTC](https://forum.qiime2.org/t/dada2-parameter-problem/17384/2 "2020-11-09T18:55:10Z")

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### Author: ![andrewsanchez](https://forum.qiime2.org/user_avatar/forum.qiime2.org/andrewsanchez/32/20160_2.png) [@andrewsanchez](https://forum.qiime2.org/u/andrewsanchez)
#### Post date: [November 9, 2020, 7:30pm UTC](https://forum.qiime2.org/t/dada2-parameter-problem/17384/3 "2020-11-09T19:30:43Z")

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Please see my response to your question in [Remove Primer in paired-end demultiplexed file](https://forum.qiime2.org/t/remove-primer-in-paired-end-demultiplexed-file/17376). **It looks like you didn't actually remove the primers** , so I'm not so sure it would make sense to run dada2 on data that still contain non-biological sequences.

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### Author: ![andrewsanchez](https://forum.qiime2.org/user_avatar/forum.qiime2.org/andrewsanchez/32/20160_2.png) [@andrewsanchez](https://forum.qiime2.org/u/andrewsanchez)
#### Post date: [November 9, 2020, 7:30pm UTC](https://forum.qiime2.org/t/dada2-parameter-problem/17384/4 "2020-11-09T19:30:47Z")

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### Author: ![system](https://forum-qiime2-org.s3.dualstack.us-west-2.amazonaws.com/original/3X/2/1/21af5fe23cb6f4579467c66a9ed94e55274ca7bd.svg) [@system](https://forum.qiime2.org/u/system)
#### Post date: [December 11, 2020, 1:30am UTC](https://forum.qiime2.org/t/dada2-parameter-problem/17384/5 "2020-12-11T01:30:50Z")

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