# Looking for advice - sequence loss in DADA2 merge **URL:** https://forum.qiime2.org/t/looking-for-advice-sequence-loss-in-dada2-merge/7662 **Category:** User Support **Tags:** dada2, merge **Created:** [January 3, 2019, 4:45pm UTC](https://forum.qiime2.org/t/looking-for-advice-sequence-loss-in-dada2-merge/7662 "2019-01-03T16:45:45Z") **Posts on this page:** 1 **Showing post:** 3
### Author: ![ChrisKeefe](https://forum.qiime2.org/user_avatar/forum.qiime2.org/chriskeefe/32/1907_2.png) [@ChrisKeefe](https://forum.qiime2.org/u/ChrisKeefe) #### Post date: [January 4, 2019, 5:19am UTC](https://forum.qiime2.org/t/looking-for-advice-sequence-loss-in-dada2-merge/7662/3 "2019-01-04T05:19:56Z")
Welcome aboard, @toobiwankenobi 👾! Thanks so much for including screencaps and complete commands. This helps a _ton_. I'll do my best to help out, but some housekeeping first - because this post was split from another post, I'm not sure whether you generated the title. If so, please be more topic-specific in future. If that's not your title, sorry! 🙊. Your denoising-stats visualization suggests that sequences are dropping out because they are failing to merge. 😢 DADA2 requires ~20 base pairs of overlap between forward and reverse reads in order to join them. If you're working with a longer amplicon, it's possible that many of your reads have insufficient overlap to merge. There's a good discussion of this in [these](https://forum.qiime2.org/t/calculate-overlap-base-pairs/4368/5) [posts](https://forum.qiime2.org/t/different-taxa-result-from-dada2-and-deblur/3381/11). Once you've determined whether this is your situation, there are quite a few posts here that discuss possible next steps. Let us know if you have trouble moving forward. If you think this is _not_ your situation, please share further sequencing details so we have a little more to work with. Thanks! Chris --- _[View the full topic](https://forum.qiime2.org/t/looking-for-advice-sequence-loss-in-dada2-merge/7662)._