Questions tagged [trimming]

To cut from the end. Trimming is often done on raw Illumina reads to discard low-quality bases or adapter sequences. Questions related to trimming algorithms, when, how to trim, trimming software.

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1answer
50 views

Telling grep to treat N as [ATCG]

Okay so I'm using grep to try and get a preview of some trimming operations that are not going as expected.. Lets say that my sequence in the FastQ file is: ATNGCNATCG What I want to do is.. ...
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0answers
24 views

FastqCleaner in R, not recognizing paired-end fastq file?

I've recently downloaded the FastqCLeaner to process paired-end fastq files locally using R (4.0.3). I'm having trouble with the shiny app. It is not uploading my second fastq file, and is repeated ...
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0answers
34 views

FastQC and Trimmomatic in Galaxy?

I am independently working on data retrieved SRA database, paired-end data as separate inputs. The proceedure I followed is, After running FastQC using Galaxy, the majority of the modules have failed....
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1answer
22 views

Trimmomatic trims most of the reverse strand

I have a paired-end data. It is from small part of human genome not a WGS or WES. I use BWA for alignment and do variant calling. Since I had some false positives I wanted to do trimming. I used ...
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1answer
171 views

How to run trimmomatic in HPC

Sorry if this has been asked before, I've done a quick search and I don't think there's an easy explanation for me to understand. I'm really new to bioinformatics/RNASEQ analysis, having only taken ...
1
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0answers
123 views

Calculating the trimming parameter when constructing an additive phylogeny

How do you calculate the trimming parameter when constructing an additive phylogeny? I think it has a relationship with the length of the shortest hanging edge, but I can't figure out how this works.
0
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1answer
592 views

What are the right parameters to trim a small RNA transcriptome with trimmomatic?

I'm having some problems with finding the right parameters to trim my small RNA Illumina reads (51 nt long) with Trimmomatic. Before trimming, one of the samples (21M reads) looks like this: So for ...
3
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2answers
748 views

Is there a safe catch-all adapter sequence for trimming?

I would like to trim/mark adapters using trimmomatic or picard MarkIlluminaAdapters from a series of Illumina Paired-End read fastqs. The fastq files may have been done using different kits or ...
3
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3answers
210 views

Tools for quality trimming at 5 prime?

I'm looking for a tool that is capable to do quality trimming at 5' end and it is configurable. For example, I can choose the quality trheshold, the read length, etc. Any recommendations? I'm ...
4
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2answers
1k views

“Sequence Duplication Levels” module still fails after pre-processing Illumina data

I want to ask about why the sequence duplication levels are high after I trimmed by using Trimmomatic? I am using the following Trimmomatic operations: ...
0
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1answer
197 views

Demultiplexing and preprocessing for custom single-nucleus Drop-seq data

I am trying to reproduce the preprocessing of paired-end sequencing reads in Lake et al. (ref. 1). First, paired-end reads were filtered out if read 1 had more than four non-T bases in the last ten ...
8
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3answers
954 views

Why does cutadapt remove low quality bases from the ends of reads only?

I use cutadapt to remove low quality bases from my Illumina reads. The algorithm only removes low quality bases from the end until it reaches a good quality base. If there is a bad quality base beyond ...
6
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1answer
798 views

How to trim adapter sequences from GSE65360 in order to map the reads?

I am trying to map single-cell chromatin accessibility data from doi:10.1038/nature14590, obtained using scATAC-seq, to the reference genome. Example paired-end reads are here. The reads contain ...
8
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1answer
1k views

FASTQC overrepresented sequences after trimming

I have a set of RNA-seq samples from different experiments (Single and Paired End, depending on the experiment). I ran FASTQC in all the samples and found overrepresented adapter sequences: I removed ...
4
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1answer
388 views

insert size pre and post trimming

I have a problem here with my rna seq data: Sequencing details: rRNA was removed, followed by cDNA preparation and generation of stranded libraries using the TruSeq Stranded Total RNA Sample Prep Kit. ...
10
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4answers
585 views

How can I systematically detect unknown barcode/adapter sequences within a set of samples?

I have often downloaded datasets from the SRA where the authors failed to mention which adapters were trimmed during the processing. Local alignments tend to overcome this obstacle, but it feels a ...