Variant Call Format

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The Variant Call Format (VCF) specifies the format of a text file used in bioinformatics for storing gene sequence variations. The format has been developed with the advent of large-scale genotyping and DNA sequencing projects, such as the 1000 Genomes Project. Existing formats for genetic data such as General feature format (GFF) stored all of the genetic data, much of which is redundant because it will be shared across the genomes. By using the variant call format only the variations need to be stored along with a reference genome.

The standard is currently in version 4.3,[1][2] although the 1000 Genomes Project has developed its own specification for structural variations such as duplications, which are not easily accommodated into the existing schema.[3] A set of tools is also available for editing and manipulating the files.[4]


##contig=<ID=20,length=62435964,assembly=B36,md5=f126cdf8a6e0c7f379d618ff66beb2da,species="Homo sapiens",taxonomy=x>
##INFO=<ID=NS,Number=1,Type=Integer,Description="Number of Samples With Data">
##INFO=<ID=DP,Number=1,Type=Integer,Description="Total Depth">
##INFO=<ID=AF,Number=A,Type=Float,Description="Allele Frequency">
##INFO=<ID=AA,Number=1,Type=String,Description="Ancestral Allele">
##INFO=<ID=DB,Number=0,Type=Flag,Description="dbSNP membership, build 129">
##INFO=<ID=H2,Number=0,Type=Flag,Description="HapMap2 membership">
##FILTER=<ID=q10,Description="Quality below 10">
##FILTER=<ID=s50,Description="Less than 50% of samples have data">
##FORMAT=<ID=GQ,Number=1,Type=Integer,Description="Genotype Quality">
##FORMAT=<ID=DP,Number=1,Type=Integer,Description="Read Depth">
##FORMAT=<ID=HQ,Number=2,Type=Integer,Description="Haplotype Quality">
#CHROM POS      ID         REF   ALT    QUAL  FILTER   INFO                             FORMAT       NA00001         NA00002          NA00003
20     14370    rs6054257  G     A      29    PASS    NS=3;DP=14;AF=0.5;DB;H2           GT:GQ:DP:HQ  0|0:48:1:51,51  1|0:48:8:51,51   1/1:43:5:.,.
20     17330    .          T     A      3     q10     NS=3;DP=11;AF=0.017               GT:GQ:DP:HQ  0|0:49:3:58,50  0|1:3:5:65,3     0/0:41:3
20     1110696  rs6040355  A     G,T    67    PASS    NS=2;DP=10;AF=0.333,0.667;AA=T;DB GT:GQ:DP:HQ  1|2:21:6:23,27  2|1:2:0:18,2     2/2:35:4
20     1230237  .          T     .      47    PASS    NS=3;DP=13;AA=T                   GT:GQ:DP:HQ  0|0:54:7:56,60  0|0:48:4:51,51   0/0:61:2
20     1234567  microsat1  GTC   G,GTCT 50    PASS    NS=3;DP=9;AA=G                    GT:GQ:DP     0/1:35:4        0/2:17:2         1/1:40:3

The VCF header[edit]

The header begins the file and provides metadata describing the body of the file. Header lines are denoted as starting with #. Special keywords in the header are denoted with ##. Recommended keywords include fileformat, fileDate and reference.

The header contains keywords that optionally semantically and syntactically describe the fields used in the body of the file, notably INFO, FILTER, and FORMAT (see below).

The columns of a VCF[edit]

The body of VCF follows the header, and is tab separated into 8 mandatory columns and an unlimited number of optional columns that may be used to record other information about the sample(s). When additional columns are used, the first optional column is used to describe the format of the data in the columns that follow.

Name Brief description (see the specification for details).
1 CHROM The name of the sequence (typically a chromosome) on which the variation is being called. This sequence is usually known as 'the reference sequence', i.e. the sequence against which the given sample varies.
2 POS The 1-based position of the variation on the given sequence.
3 ID The identifier of the variation, e.g. a dbSNP rs identifier, or if unknown a ".". Multiple identifiers should be separated by semi-colons without white-space.
4 REF The reference base (or bases in the case of an indel) at the given position on the given reference sequence.
5 ALT The list of alternative alleles at this position.
6 QUAL A quality score associated with the inference of the given alleles.
7 FILTER A flag indicating which of a given set of filters the variation has passed.
8 INFO An extensible list of key-value pairs (fields) describing the variation. See below for some common fields. Multiple fields are separated by semicolons with optional values in the format: "<key>=[,data]".
9 FORMAT An (optional) extensible list of fields for describing the samples. See below for some common fields.
+ SAMPLEs For each (optional) sample described in the file, values are given for the fields listed in FORMAT

Common INFO fields[edit]

Arbitrary keys are permitted, although the following sub-fields are reserved (albeit optional):

ancestral allele
allele count in genotypes, for each ALT allele, in the same order as listed
allele frequency for each ALT allele in the same order as listed: use this when estimated from primary data, not called genotypes
total number of alleles in called genotypes
RMS base quality at this position
cigar string describing how to align an alternate allele to the reference allele
dbSNP membership
combined depth across samples, e.g. DP=154
end position of the variant described in this record (for use with symbolic alleles)
membership in hapmap2
membership in hapmap3
RMS mapping quality, e.g. MQ=52
Number of MAPQ == 0 reads covering this record
Number of samples with data
strand bias at this position
indicates that the record is a somatic mutation, for cancer genomics
validated by follow-up experiment
membership in 1000 Genomes

See also[edit]

  • The FASTA format, used to represent genome sequences.
  • The FASTQ format, used to represent DNA sequencer reads along with quality scores.
  • The SAM format, used to represent genome sequencer reads that have been aligned to genome sequences.
  • The GVF format (Genome Variation Format), an extension based on the GFF3 format.

The VCF specification is no longer maintained by the 1000 Genomes Project. The group leading the management and expansion of the format is the Global Alliance for Genomics and Health (GA4GH) Large Scale Genomics Work Stream file format team[5],

External links[edit]

  • An explanation of the format in picture form
  • Free, graphical tool to inspect, search, split and merge VCF files on OS X
  • Ossola, Alexandra (20 March 2015). "The Race to Build a Search Engine for Your DNA". IEEE Spectrum. Retrieved March 2015. Check date values in: |access-date= (help)


  1. ^ "VCF Specification" (PDF). Retrieved 20 Oct 2016.
  2. ^ "Specifications of SAM/BAM and related high-throughput sequencing file formats". Retrieved 24 June 2014.
  3. ^ "Encoding Structural Variants in VCF (Variant Call Format) version 4.0 | 1000 Genomes". Retrieved 20 October 2016.
  4. ^ "VCFtools from". Retrieved 20 October 2016.
  5. ^ "Bio-IT World". Retrieved 2018-10-26.