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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16
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2answers
395 views

How can I call structural variants (SVs) from pair-end short read resequencing data?

I have a reference genome and now I would like to call structural variants from Illumina pair-end whole genome resequencing data (insert size 700bp). There are many tools for SV calls (I made an ...
11
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3answers
15k views

How to subset samples from a VCF file?

I have VCF files (SNPs & indels) for WGS on 100 samples, but I want to only use a specific subset of 10 of the samples. Is there a relatively easy way to pull out only the 10 samples, while still ...
11
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2answers
271 views

Do variant calls change when you call from CRAM?

We're considering switching our storage format from BAM to CRAM. We work with human cancer samples, which may have very low prevalence variants (i.e. not diploid frequency). If we use lossy CRAM to ...
9
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3answers
1k views

Selecting sites from VCF which have an alt AD > 10

I have high-depth variant calling created using the HaplotypeCaller with --output_mode EMIT_ALL_SITES I'm interested in finding all sites (regardless of genotype ...
9
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2answers
255 views

calling diploid SNVs from long reads

I'd like to call diploid SNV variants from long-reads data (~80SMRTcells PacBio). I have generated a draft reference genome for an indivudual from a heterozygous (~4%) species (Canu+Haplomerger2). ...
8
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4answers
905 views

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 ...
8
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2answers
7k views

Converting a BAM file into VCF

I have NGS illumina RNA-seq reads from M. musculus (mm10). I am trying to find variants along the strand portion of the reads in the refseq (mm10). I mapped a pair of sequence files and generated a ...
8
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3answers
2k views

How to quickly determine mutations in a read of a sam file?

After DNA sequencing, I generated a sam file through alignment of a fastq file. Before using well known variant calling programs (eg. Annovar etc.), I want to pick some reads and know what kinds of ...
8
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2answers
4k views

Tools to do VCF to MAF and MAF to VCF conversion?

Normally, I would use the vcf2maf scripts to convert a VCF to a MAF (or vice versa). This is great software, but on my system, perl scripts with dependencies are easy to break. (Here it uses VEP.) ...
8
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2answers
6k views

Why Ti/Tv ratio?

I'm interested in the transition/transversion (Ti/Tv) ratio: In substitution mutations, transitions are defined as the interchange of the purine-based A↔G or pryimidine-based C↔T. Transversions are ...
8
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3answers
356 views

Books on bioinformatics algorithms

I'm looking for a book about bioinformatics algorithms, such as alignment, BLAST search, and variant calling. I'm hoping reading about this subject will give me a deeper understanding of the ...
8
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4answers
1k views

Is there a point in recalibration of scores for variant calling?

The most variant calling pipeline GATK include a Base Quality Score Recalibration (BQSR) which requires a list of known variants. Recently, some work has been done for reference-free recalibration of ...
7
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3answers
250 views

How to detect a mutation and predict its consequence?

I read lecture notes about mutations, and wondered what kind of algorithms are there to detect mutations? How do we know if the gene is mutated or whether it is a sequencing error? I saw this thread ...
7
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3answers
2k views

How can I count the number of reads that support a variant in a bam file?

I am calling variants from a human sample using bwa mem to align the reads and gatk to call the variants. I'm trying to understand why a specific variant was not called in my sample. I have checked ...
7
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2answers
274 views

variant calling on ChIP-seq style data: samtools mpileup with minimal filters

I am running samtools mpileup (v1.4) on a bam file with very choppy coverage (ChIP-seq style data). I want to get a first-pass list of positions with SNVs and their frequency as reported by the read ...
7
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1answer
145 views

How can I speed up INDEL calling/correction on BAM files?

The samtools mpileup command has quite a neat feature that it is able to correct mapping errors associated with misalignment of INDELs. By default, the ...
6
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2answers
829 views

What is indel calling and what is its purpose?

I'm having a difficulty in grasping the general purpose and concept of indel calling. What exactly is this process?
6
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2answers
2k views

How do I generate a variant list (i.e. VCF file) using Illumina reads from a human genome?

This is a problem I have to solve frequently, and I'd be interested in knowing what other methods people use to solve the same problem. About twice a year, I get asked to determine variants from ...
6
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2answers
180 views

Why chose CNN for a variant caller

Google released their variant caller DeepVariant which won the highest SNP performance award in the Precision FDA Truth challenge (99.999% accuracy). From the linked github repo, we see that ...
6
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1answer
1k views

Merge 2 VCFs from different variant callers

I am working with WES data for detection of somatic variants and I have used two variant callers because no variant caller is complete in itself. I have used GATK Haplotypecaller for small variants ...
6
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2answers
342 views

How to correctly call a VCF file using damaged DNA? (IonTorrent & FFPE)

EDIT: I am updating this question to make it more specific to my issue. For context - original question prior to edit: How do I obtain a deamination metric when doing the variant calling using the ...
5
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3answers
1k views

Somatic tumor only variant calling?

I'm evaluating possibilites for somatic tumor variant calling without paired-normal samples. I'm aware of the consequences without a normal sample. All the popular variant calling tools such as ...
5
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6answers
1k views

Identifying Indels from Chromatograms

I have around 100 chromatograms (.ab1 files) from Sanger sequencing a genome at loci believed to have an indel. I'm new to interpreting this kind of data in ...
5
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2answers
1k views

No variant found using GATK 4.0 HaplotypeCaller

I am doing variant calling on RNA-seq datasets from wheat which is hexaploid,the binary alignment (BAM) files were created using STAR version 2.6.0c and variant calling was done using GATK 4.0 ...
5
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1answer
512 views

Tool or script to parse annotated VCF files

I've annotated VCF files using snpEff and looking for a tool or script to parse the VCF file and clean up the file to make it interpretable for a biologist.
5
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1answer
342 views

Can a data file in VCF format be converted into FASTA?

I'm considering purchasing the 'MyGenome' product by Veritas Genetics to analyze my genome for a project. I'd like the data to be in FASTA format, but Veritas only provides VCF data. Is it possible to ...
4
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2answers
629 views

Why are there missing calls in a VCF file from exome sequencing?

My data is a VCF file generated from an exome sequencing variant call pipeline. I'm not very familiar with the sequencing and variant calling process. I noticed that there are some missing genotypes, ...
4
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1answer
212 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
709 views

GATK CombineVariants complains the contig order in the VCF files

I have called variants on two strains of C. elegans separately. I now want to merge the VCF files into one using the following code: Create a sequence dictionary of the reference sequence Sort the ...
4
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1answer
261 views

Keep Format and Individual fields when annotating VCF with VEP

I'm currently updating my Variant Calling Pipeline by switching the VCF annotating software from Annovar to VEP for a variety of regions, not least how easy it is to annotate with HGVS notation and ...
4
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1answer
208 views

Old versions of the reference genome and dbSNP

For benchmark purposes I’m trying to find an old version of the human reference genome (pre-GRCh37) and a matching version of dbSNP. Unfortunately it appears as though older versions of dbSNP aren’t ...
4
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1answer
131 views

Remove variants that do not map to human genome

[This question was also asked on Biostars] 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 ...
4
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3answers
1k views

Issues performing variant calling with GATK

I am trying to perform variant calling on a BAM file generated through STAR version STAR_2.6.0b for wheat genome using GATK haplotypecaller as follows: ...
3
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4answers
1k views

How to run same command on multiple files?

Hi im doing Variant calling on fastq files for which i have 4000 fq files and the variant calling are done in different 9 steps. Each step generate different files that are output to next steps. So ...
3
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3answers
3k views

Find overlap between VCF files

I have two VCF files and I want to compare the missing rate in each of them, but I want to only look at sites that are present in both files. How could I go about getting a list of positions that are ...
3
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3answers
94 views

Which gene I should select from this qqplot [closed]

I have a qqplot of my whole genome sequencing data; A plot is for showing possibly significant driver genes. I tried to read about qqplot though but people only say about the skewedness while I want ...
3
votes
1answer
343 views

Output from vcftools missingness

I'm new to data filtering on vcf data and vcftools. I performed variant calling on my dataset, CHR22, homo sapiens. I'd like to remove sites that are missing in more than 5% of individuals. ...
3
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1answer
3k views

Increase number of threads for GATK 4.0 HaplotypeCaller

I am using GATK version 4.0, I tried to use multiple threads for calling variants using HaplotypeCaller using following command ...
3
votes
1answer
91 views

Human SNP databases other than dbSNP

I'm working on a project to identify variants as being either germline or somatic based on nearby SNPs, and I was wondering if there were any databases of SNPs for Homo sapiens other than dbSNP? I'm ...
3
votes
1answer
38 views

Database for germline copy number variations in cancer

I am interested in looking at germline copy number variations in individuals that are at high risk of developing cancer. Are there any databases where I can look, if a CNV seen in our test case has ...
3
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2answers
244 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 ...
2
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2answers
39 views

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 ...
2
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1answer
76 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 ...
2
votes
1answer
177 views

What does "motif 2 bp or longer" mean?

I'm reading a preprint on a new somatic variant discovery tool, and the first sentence of the Discussion section has me confused. Across the four datasets analyzed in this study, we discovered that ...
2
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1answer
85 views

Why does IGV turn a VCF QUAL of "." into -10?

IGV is turning QUAL "." into -10 from this VCF of structural variations. I'm wondering if this means anything or if I should report a bug to the IGV devs. Here's a row from a VCF: ...
2
votes
1answer
64 views

Knowing which positions are variants

Let's say I'm sequencing a donor, and I have 20X coverage. And let's say all the reads covering a particular base has the same allele at the position. Then, is that position considered a "variant" ...
2
votes
1answer
34 views

GRCm37-designed exon target enrichment, which reference to use?

I have exomes from 24 individual mice. The exomes are the product of Roche's SeqCap EZ HyperCap target enrichment kit. I see that the mouse exome design comes from mm9/NCBI37, the previous major ...
2
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1answer
588 views

Can I pilon-polish long reads with Illumina short reads to improve structural variant detection?

I have pacbio Sequel data at 50 x coverage for a strain of animal. I would like to find structural variants compared to the reference genome sequence. At the moment, I align my reads to the reference ...
2
votes
1answer
59 views

IonTorrent variant caller failing, lack of ZM: tags in BAM files

I have a lot of IonTorrent sequencing data in BAM format that I want to call variants on, using the IonTorrent variant caller. However, for some of the BAM files (for about 12 samples out of ~150), ...
2
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0answers
31 views

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 ...