Skip to main content

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.

Filter by
Sorted by
Tagged with
3 votes
2 answers
51 views

Issues with adapter trimming (Trim Galore)

I am new to coding and especially new to bioinformatics so I am sorry if this is a dumb question. Nevertheless, I am attempting to run Trim Galore! to trim my paired RNAseq data, there are no error ...
0 votes
1 answer
70 views

Paired end reads with different read lengths

I downloaded some raw RNA-seq reads from NCBI using the sra-toolkit (Accession numbers: SRR2053159-64). The reads were generated using ABI SOLiD, and in colour space. I downloaded them in base space ...
1 vote
0 answers
83 views

Can files with different R1 and R2 lengths be trusted?

I received paired end amplicon sequence from a LAB with different lengths for R1 (320) and R2(280). Should I trust this lab to sequence other samples? Also, I had to do a trimming over the R2 at 220(...
1 vote
0 answers
106 views

Steps for trimming aligned peptides using Trimal

I am trimming the aligned peptide sequences and back translating them to codon using Trimal. Here i am using following cmd's: ...
1 vote
1 answer
301 views

Primer trimming-fasta files

My goal: I want to trim off the primers (Forward : CGAGAAGACCCTRTGRAGCT, Reverse : GTTGGGGYGACCNYGG) from a fasta file with a lot of dna sequences allowing for some (e.g. 3) mismatches (identity). ...
4 votes
1 answer
47 views

Trim reads 1kb upstream of sequence

I need a quick way to trim multiple reads in a FASTA file. I need to trim everything that is 1kbp upstream of this sequence ...
3 votes
1 answer
150 views

Does cutadapt trim trailing N's first and then use max_n to filter reads?

Background I want to trim leading and (likely just) trailing N's from my WES (Illumina NextSeq500) reads with cutadapt (--trim-n)...
1 vote
1 answer
274 views

Using sickle for quality trimming

I am using sickle package from bioconda to trim my reads from the Illumina Miseq. When I tried following code, it failed to run ...
1 vote
1 answer
1k views

Searching for adapter sequences in FASTQ files - metgenomics

I have recently received some metagenomic data from 16S rrna sequencing. The sequencing company claim to have removed primers, however not adapter sequences. Please note that the files have been ...
2 votes
1 answer
208 views

When using cutadapt, can I specify an R2 adapter as optional when I have a required R1 adapter?

I'm using cutadapt 3.5 to trim adapters and perform some filtering on paired-end data. Both R1 and R2 sequences have 3' adapters that might be found depending on the sequence length, but R1 also has ...
7 votes
1 answer
685 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. ...
1 vote
0 answers
195 views

Why is cutadapt discarding some paired end reads?

So, I am using cutadapt to remove two primers from some paired end reads. I have 2 files for each sample, i.e. sample_R1.fastq and sample_R2.fastq. I have primer_1 and primer_2 and both of them can be ...
1 vote
1 answer
237 views

fastq file format unknown

I have paired-end fastq files some of which seem to be in a weird format (from a collaborator, not a public database). When I cat the file I get what seem to me to ...
4 votes
1 answer
89 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.. ...
0 votes
0 answers
81 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 ...
1 vote
0 answers
210 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....
1 vote
1 answer
136 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 ...
1 vote
0 answers
296 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 votes
1 answer
590 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 ...
0 votes
1 answer
2k 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 votes
3 answers
347 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 ...
3 votes
2 answers
1k 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 ...
4 votes
2 answers
3k 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 votes
1 answer
235 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 votes
3 answers
2k 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 ...
7 votes
1 answer
1k 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 ...
9 votes
1 answer
2k 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 ...
12 votes
4 answers
1k 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 ...