# After Trim galore!, fastqc show the seuqence length is 20-151

**URL:** <https://help.galaxyproject.org/t/after-trim-galore-fastqc-show-the-seuqence-length-is-20-151/8996>\
**Category:** usegalaxy.org support\
**Tags:** troubleshooting, transcriptomics, quality-control, rna\_star\
**Created:** [November 9, 2022, 11:16am UTC](https://help.galaxyproject.org/t/after-trim-galore-fastqc-show-the-seuqence-length-is-20-151/8996 "2022-11-09T11:16:22Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Jiahui](https://sea2.discourse-cdn.com/flex020/user_avatar/help.galaxyproject.org/jiahui/32/3560_2.png) [@Jiahui](https://help.galaxyproject.org/u/Jiahui)\
**Post date:** [November 9, 2022, 11:16am UTC](https://help.galaxyproject.org/t/after-trim-galore-fastqc-show-the-seuqence-length-is-20-151/8996/1 "2022-11-09T11:16:22Z")

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Hi all, I run fastqc and multiqc and found that my RNA-seq has adaptors exists, after using trim galore! I run fastqc to see if the QC could be better, but the results show that the sequence length becomes a range that is from 20-151. I need a specific sequence length (that should be 150, from the fastqc result before trim galore!) to do RNA-star. But now it turned out to be a range, can anyone help me? btw, I tried cutadapt, but after cutadapt, I run fastqc, and it shows the adaptor is still there.

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**Author:** ![jennaj](https://sea2.discourse-cdn.com/flex020/user_avatar/help.galaxyproject.org/jennaj/32/27_2.png) [@jennaj](https://help.galaxyproject.org/u/jennaj)\
**Post date:** [November 11, 2022, 1:28am UTC](https://help.galaxyproject.org/t/after-trim-galore-fastqc-show-the-seuqence-length-is-20-151/8996/2 "2022-11-11T01:28:13Z")

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Hi @Jiahui

Sequence reads are often represented by a range of lengths. **RNA-Star** is not restricted to 150 bases. But if you do want to filter by length for some reason, **Trim Galore!** has an advanced setting named `Discard reads that became shorter than length N`.

Maybe these tutorials will help more.

> **[Galaxy Training: Quality Control](https://training.galaxyproject.org/training-material/topics/sequence-analysis/tutorials/quality-control/tutorial.html)**
>
> Analyses of sequences

> **[Galaxy Training: Mapping](https://training.galaxyproject.org/training-material/topics/sequence-analysis/tutorials/mapping/tutorial.html)**
>
> Analyses of sequences

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**Author:** ![jennaj](https://sea2.discourse-cdn.com/flex020/user_avatar/help.galaxyproject.org/jennaj/32/27_2.png) [@jennaj](https://help.galaxyproject.org/u/jennaj)\
**Post date:** [December 20, 2023, 9:35pm UTC](https://help.galaxyproject.org/t/after-trim-galore-fastqc-show-the-seuqence-length-is-20-151/8996/3 "2023-12-20T21:35:41Z")

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