Questions tagged [variant-calling]

The process of discovering variants in individuals starting from sequencing reads. Can be subdivided into germline variant calling and somatic variant calling. Can also be used for the more specific process of finding variants starting with reads aligned to a reference genome (SAM/BAM files).

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How do I generate a variant list using Illumina reads from a Salmonella genome?

I am planning on performing phylogenetic analysis of Salmonella specimens using WGS data from PulseNet and GenomeTrakr, for the purpose of public health surveillance & to provide context for ...
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Benchmarking for variant identification using RNA-seq data

I am in need to benchmark the variant identification pipeline which uses RNA seq data alone without any matched-normal. I would like to know the reference dataset (and the pipeline on which the ...
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Compare VCF files

I have two strains, X and Y, and I would like to compare the variants found in both. I have my own parent strain, Z, that was sequenced and assembled to be used as the reference genome. I first ...
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Name this alternative INDEL format

I have recently been working with variants which are represented in a non-standard format. This alternative format uses a period instead of prefixing variants with a reference base. What is this ...
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Find SNPs in yeast genomes

I'm a new Bioinformatic scientist working for a yeast genetics company. Objective To create a database of yeast genomes from NCBI and identify SNP variants. In my pipeline FastQC, Trimmomatic, BWA ...
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Difference between pileup and mpileup in VarScan and samtools

I'm going to call variants with VarScan from a pileup files created with samtools. I realized that there are in general two major possibilities to call variants, pileup as well as mpileup. The VarScan ...
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snakemake tutorial stuck in basics-step-5 (variant calling)

I am learning to use snakemake. I am following the tutorial (https://snakemake.readthedocs.io/en/stable/tutorial/tutorial.html). In the section called "Basics", steps 1 to 4 worked well, ...
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somatic SNV tool for ONT samples

I'm looking for a tool to call somatic single nucleotide variations on reads from an Oxford Nanopore Technologies (ONT) run. I have both tumor and normal samples and have already aligned them to a ...
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How deep variant and others preprocessed insertion and deletion for extracting candidate variant?

I am trying to build a model for variant calling,but I am a bit confused how to pre-process the reads that has insertion and deletion and align them with reference? Should I add something to the ...
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Reference variant detected as altered one in bam file

I received (from manufacturer) several .bam files and I used four callers (samtools, freebayes, haplotypecaller, deepvariant) to find some sequence variants. In obtained .vcf files, I took a closer ...
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What is the best tools to find all the somatic mutations?

I am a beginner in this field. I would like to know which is the best way to get all the mutations from a certain sample. At this point, I am considering using GATK (here) and Maftools (here). I don't ...
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Detect mutation context in a read of a sam file

After sequencing (Illumina) of some DNA, I generated a sam file through alignment of a fastq file (using Bowtie2). Instead of using variant calling programs, I want to know the specific variances, ...
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Range of values for VAF in heterozygous genotype

(VAF = variant allele frequency) This question follows from this one. What is the expected range of values for VAF of mutations with heterozygous genotype (i.e., 0/1 or 0|1)? Is it possible to have 0% ...
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Assess ploidy estimation through SNV and CNV results

I want to assess ploidy estimation (i.e., diploid vs tetraploid) in a set of samples for which I have both results from the variant caller (i.e., SNVs) and from the copy number caller. What are the ...
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GATK variant filtration using "SelectVariants" and use of JEXL queries

How to do variants selection in some corner cases using GATK and JEXL expressions? I am following the guidelines given in this links for variant selection for some specific cases are not as much ...
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When can we have duplicated variants in a VCF file, excluding artifacts?

I read these two questions on duplicated VCF variants: 1, 2. However, it is not entirely clear to me when duplicated variants can arise (excluding merging artifacts). I want to understand if ...
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Nanopore variant calling

So far I haven't done any variant calling as such. Nanopore I have used for 16s microbiome data. Now My question/doubt so how do I proceed for nano-pore virus sequencing data Steps: I get fast5 files ...
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Meaning of order of alleles in VCF GT field for unphased genotypes

Order of alleles in genotype field (on VCFs) can be used to infer haplotypes However, what about unphased genotypes? I have a VCF file where I only have unphased genotypes: ...
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Convert VCF file to mpileup.txt

I am working on an iterative analysis that uses orthologous pipelines that require mpileup.txt files as input for a visualization step. This requires me to convert VCF files to mpileup.txt. This ...
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315 views

How do I call variants using BCFTools without piping mpileup file?

I need to call variants on a large number of reads using both VarScan2 and BCFTools. Both of these variant calling tools use <...
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Fastest way to count where two bam files are homozygote reference (inverted variant calling)

Maybe I'm having a brain-freeze so excuse me if this is a waste of everyone's time... I am working with an organism with ~700Mb genome. I have bam files of two individuals that are whole genome ...
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7 votes
4 answers
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Are variant calling files personally identifiable information?

This question is to be read in the context of data protection. It seems to be common understanding that the whole genome sequence of an individual is personally identifiable, non-anonymizable ...
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1 answer
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Consensus sequence from vcf file

I am generating a consensus sequence for SARS-Cov-2. I am visually inspecting every candidate SNP in a pileup. Sometimes I find that there are two consistent variants for the same position, but I can ...
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Detecting SARS-CoV-2 variants from the mixed virus population

I have a fastq file from Nanopore sequencing data that contains reads from both the UK and South Africa variants of SARS-CoV-2. The variants are identified by three key mutations in the receptor-...
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Solutions to reference bias issue

I've recently learned about the reference bias issue - inability to properly map NGS reads in certain genomic regions caused by the fact that our standard genomic references are linear and do not ...
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Calling for one specific SNP from multiple sequencing runs

Just learning the basics of bioinformatics and bash shell scripting. Is there a correct way to search for a specific allele with one or even multiple sequencing runs? I am searching for prevalence of ...
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854 views

Can an alternate allele be more common than a reference allele?

I'm trying to analyze data from a genotype-phenotype association study. The genotype data is stored in csv files that record for each variant site and each subject, the alleles that the subject has at ...
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SnpEff not correctly annotating multiple-nucleotide polymorphisms

I have some SARS-CoV-2 sequencing data that I'm trying to annotate with SnpEff, however SnpEff doesn't appear to be recognizing multiple adjacent SNPs within the same codon and correctly calling them ...
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Why is there no GT-entry in my .vcf file from bacteria

I mapped raw reads obtained from an E. coli genome (.fastq file) to my reference genome. Next, I exported the .vcf (variant calling file), which looks something like the header example shown below (...
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genotyping or variant calling in R

Are there any good options for calling variants or even just a pileup from R? R is not ideal for this, but I'd like to integrate with other functions. I found deepSNV::bam2R which roughly does what I ...
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Supplementary aligments in VAF

This question has also been asked on Biostars I have a doubt, are supplementary alignment usually considered when the variant allele frequency is calculated? Thanks a lot. In my case I have some ...
2 votes
1 answer
105 views

Are there open-sourced graph-based variant callers?

I would like to compare GATK with graph-based variant callers. I have seen the Fast and accurate genomic analyses using genome graphs paper from SevenBridges and the paragraph tool by Illumina, though ...
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Finding SNP/Indel Markers of Interspecific Variation

This is a revised version of my original question, edited to include the portions already answered by @Maximilian Press. Goal: Find SNP and indel alleles which are fixed between but lack polymorphism ...
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Joint variant calling of two sample sets with different coverages (~5x vs ~25x)

Let's say 50 samples were sequenced at 25x. After a while, the group realizes that the experiment is under-powered and adds 100 samples more, but at a coverage of 5x. I'm talking about WGS. The ...
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Calling variants with DeepVariant on targeted NGS sequencing (custom library)

I am seeking advice regarding DeepVariant analysis. To avoid false positives I'm using several variant callers and then the resulting common set will be considered as TP variants. One of the callers ...
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How can I get or create a reference genome for Bacteria?

I am a computer engineer and nowadays trying to grasp some concepts of Bioinformatics particularly, reference genomes and genomic variants. My aim is to find the effect of sequence features on variant ...
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2 answers
628 views

How does DeepVariant construct RGB images from DNA sequences?

DeepVariant is a pipeline to call genetic variants from DNA sequencing data. A major step, before feeding the CNN, is to translate these DNA sequences into images. It's unclear why and how Google ...
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Download or create VCF from Human Genome Diversity Project (HGDP)

I can't seem to find HGDP data in VCF format. Does anyone know where I can download it from? Perhaps there a Snakemake pipeline for calling VCFs from this data?
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Non-exome variants called from whole-exome sequencing data

I'm working on rather standard whole-exome sequencing data and treat it the same as whole-genome sequencing data (aligning it to the full GRCh38 reference assembly and calling variants with no exome-...
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How can I extract all known mutations of my BAM (or SNP/INDL files)?

I am using a Genome Explorer tool to see all the mutations on my own DNA. My particular interest is on listing the variants and get their names/ids. Here are a few screenshots: You can see that ...
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Best practice to perform a functional analysis on a set of VCFs from a cohort of patients

I am confused about how to perform a functional analysis after a variant calling on a cohort of patients. I have anotated all vcfs and filter them in order to get only those deleterious variants. I ...
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Filtering VEP annotation file

I am filtering a VEP annotated vcf, trying to maintain just those variants classified as deleterious by SIFTand as damaging (probably or possibly included) by ...
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Pindel has an extremely large output

I am wondering if I am doing something wrong here. I ran Pindel (alongside two other structural variant [SV] callers) on four WGS samples. The two other callers ...
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No MQ tags in VCF files

To call minority variants in my Mtb sequences I'm using a pipeline of ...
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How can I find the position of every mutation where the Allele Frequency is greater than X, in regards to a reference such as Hg19?

I have a Human genome sequenced in a BAM file (along with other files with the indels, snps, cnvs). I want to find every mutation with regards to the reference Human genome. However the majority of "...
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What samples can be used for a Mutect2 Panel of Normals

I'm working on calling somatic variants from solid tissue tumors. I have one normal and one tumor sample for each patient. I plan to use Mutect2 to call somatic variants after preprocessing the data ...
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2 answers
60 views

Variant calling for a subset of genes using whole gneome sequencing data

I have few 100 raw fastq files from whole-genome sequencing data and I would like to map these files to a set of genes only (and not whole genome) so as to find SNP's associated with them. Can anyone ...
2 votes
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Detection of CNV(InDel) of intermediate size

My impression is that small InDel (a couple of bp) is identified through cigar string in BAM and typical CNV (at least thousands of bp) is detected through read depth. What about InDel or CNV with ...
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Interpreting MultiQC plot of GATK BaseRecalibration data?

I'm using GATK4 to build a somatic variant calling pipeline. The pipeline uses MultiQC to aggregate quality control data, and one of the QC measures reported is base quality score recalibration from ...
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Help with the definitions of fields in a VCF output by Strelka

In Strelka vcf in INFO column we have these ...
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