Questions tagged [quality-control]

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1answer
24 views

Metagenomic shotgun data with internal control

For 24 human stool samples I have metagenomic shotgun reads from an Illumina platform. The reads were filtered and mapped against a bacterial species library and specific maps to species were kept and ...
2
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1answer
62 views

Oxford Nanopore mapping Quality and sequencing error

I'm analyzing some Oxford Nanopore sequencing reads, with several articles stating the sequencing error is between 5% and 15%. Since its 1D and not 1D^2 sequencing i would assume the sequencing error ...
1
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1answer
44 views

Subset a multisample VCF file

I need some help with GATK. I have a multisample vcf file containing 18125 samples. After performing PCA I have around 303 samples as outliers and I wanted to remove these samples from my multisample ...
3
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1answer
81 views

Remove variants that do not map to human genome

I received an hg38 VCF file that's had variants imputed with 1000 genomes. I've encountered some issues with the VCF; REF alleles that do not align to a reference genome, ALT alleles that do not ...
5
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0answers
24 views

Help with 1D^2 library shearing

I've done my 1st trial of 1D^2 whole genome sequencing using LSK-SQK308 kit with R9.5 flowcell. Without doing library fragmentation, I encountered the unexpected library shearing during sequencing. ...
1
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0answers
40 views

“Bad substitution” error while trimming adapters [closed]

I have this script to trim adaptors from my fastq sequencing files for PAIR in $(fastq | sed 's/_R.//g' | uniq) I am gitting this error: bad substitution Could ...
3
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3answers
107 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
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1answer
453 views

Significance and timing of “mux scans”

I'm using MinIONQC to do quality control on some ONT data. The software plots several read characteristics over time (hours passed during the sequencing process). These plots contain several vertical ...
5
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3answers
1k views

Bash scripting FastQC for multiple fastq files in multiple directories

I am completely new to bioinformatics so I'm looking to learn how to do this. I have multiple directories with fastq files: E.g; 10 Directories with each time series, each with Treatment and control ...
0
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0answers
32 views

Quality checking benchmarks for clustering

I'm currently working with several RNAseq datasets from the ENCODE database. My approach to assessing the quality of the data, i.e, reproducibility is by automating the assessment of expression ...
8
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3answers
670 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 ...
1
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1answer
105 views

Optimal design for an RNA-seq experiment with ERCC RNA Spike-In Control Mixes

I am planning an experiment on gene expression. I have 6 conditions and 3 replicates in each condition. I would like to use ERCC spike-in mixes for quality check: lower limit of detection, dynamic ...
2
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1answer
77 views

How hard is it to clean and QC gene expression microarray data?

I am a PhD student working on developing ideas for my dissertation papers. One of my planned papers will be working with some (human) gene expression data. I have had a class on working with gene ...
7
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2answers
3k views

Are mitochondrial genes to exclude in scRNA-seq such as ribosomal genes?

In this answer, it is stated that ribosomal genes should be excluded prior to normalization in scRNA-seq as contaminants. Do mitochondrial genes have to be excluded as well? I plotted the top 50 ...
0
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1answer
93 views

What is the --rev_comp_mapping_barcode parameter in the QIIME1 script extract_barcodes.py?

I'm using the QIIME1 scripts extract_barcodes.py to extract barcodes from a dual-indexed MiSeq library, and then demultiplex my reads using split_libraries_fastq.py. I have been having trouble ...
11
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2answers
2k views

determining doublets in single-cell RNA-seq

Doublets are a known problem with scRNA-seq experiments, where 2 or more cells are sometimes captured instead. To determine their presence, there are studies that mix multiple species (such as human ...
5
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2answers
1k views

What are doublets in single cell RNA-seq data?

I am reading The Tabula Muris Consortium et al. (pp). In some organs, cells with more than 2 million reads were also excluded as a conservative measure to avoid doublets. How exactly is a “doublet”...
4
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1answer
172 views

Where can I get the population allele frequency vcf file?

I want to use GATK to estimate cross-sample contamination for Whole Genome Sequencing data. The specific tool is ContEst and it is run with: ...
4
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2answers
273 views

Error rate setting in Canu error correction

I want to use Canu to correct my nanopore long read (version: MinION R9.5), but I am not quite sure how to set the correctErrorRate. Should I follow the Canu manual (Nanopore R7 2D and Nanopore R9 1D ...
6
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3answers
2k views

Removing PCR duplicates in RNA-seq Analysis

After reading some of the forum posts in Biostar and SeqAnswers I find it very confusing whether to filter out the duplicate reads from aligned files or not. As far I understand it's very difficult to ...
4
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5answers
456 views

QC measures for NGS sequencing

What are good means for performing quality control (QC) or NGS reads? I'm aware of: FastQC NGS Screen Kraken (e.g., for screening against contaminants) What are other popular means for such QC?