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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15
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2answers
359 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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2answers
199 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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2answers
213 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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3answers
863 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 ...
8
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3answers
263 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
873 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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2answers
4k 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 ...
7
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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 ...
7
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2answers
205 views

How to detect a mutation and predict its consequence?

I read a lecture notes about mutations, what kind of algorithms are there to detect mutations? How do people know if the gene is mutated or whether it's a sequencing error? I saw this which is ...
7
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2answers
235 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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2answers
3k 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.) ...
7
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2answers
4k 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 ...
7
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1answer
139 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
651 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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3answers
1k 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 ...
6
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2answers
1k 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
170 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
votes
1answer
905 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
241 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
912 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
665 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
votes
3answers
7k 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 ...
5
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2answers
789 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
418 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
votes
1answer
285 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
473 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
197 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
563 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
votes
1answer
229 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
121 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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3answers
661 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
votes
4answers
601 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
81 views

Which gene I should select from this qqplot

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
183 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
2k 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
34 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
votes
1answer
82 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
109 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 ...
2
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3answers
1k 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 ...
2
votes
1answer
154 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
78 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
39 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
30 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
549 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
44 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
29 views

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 ...
2
votes
0answers
41 views

NA12878 equivalent for somatic variant calling [duplicate]

I'm building a somatic variant calling pipeline with snakemake. The pipeline is hosted on Github, and I'd like to use Travis CI for continuous integration testing. ...
2
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0answers
75 views

How snippy makes MSA-like aligned fasta output from multiple samples?

From the log file it seems snippy doesn't do assembly. It only does mapping: fastq --> SAM --> BAM --> VCF --> consensus_seq/snps But if multiple ...
1
vote
2answers
119 views

VEP output SIFT_score unclear

We have been experimenting with VEP (Variant Effect Predictor). One of the meta data attributes that we are interested in is the SIFT score, indeed when we apply the dbNSFP plug we get a column ...
1
vote
1answer
24 views

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 "...