Variant Allele Fraction
Variant Allele Fraction - Related Videos
10:17
An Allele-specific Gene Expression Assay to Test the Functional Basis of Genetic Associations
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Cited by 2 •
2010
Genetic associations often remain unexplained at a functional level. This method aims to assess the effect of phenotype-associated genetic markers on gene expression by analyzing cells heterozygous for transcribed SNPs. The technology allows accurate measurement by MALDI-TOF mass spectrometry to quantify allele-specific primer extension products.
14:06
Detection of Rare Genomic Variants from Pooled Sequencing Using SPLINTER
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Cited by 10 •
2012
Pooled DNA sequencing is a fast and cost-effective strategy to detect rare variants associated with complex phenotypes in large cohorts. Here we describe the computational analysis of pooled, next-generation sequencing of 32 cancer-related genes using the SPLINTER software package. This method is scalable, and applicable to any phenotype of interest.
04:32
Chip-in-a-Tube-Based Digital PCR for Quantification of Single Nucleotide Variants
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2025
This video demonstrates the utility of digital PCR in a chip-in-a-tube format for the detection of single nucleotide variations in DNA samples. A single PCR reaction is partitioned into chambers that act as independent PCR reactions, and the detection of fluorescence signals from the amplified targets in the chambers is used to compute the frequency of the variant allele in the sample.
02:19
Multiple Allele Traits
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2021
For the same gene multiple alleles can interact to influence phenotypes like the shape and protein composition of an individual cells.By studying allele interactions on the molecular and cellular levels researchers can understand the resulting phenotypes and complications of human conditions like sickle cell trait, improving treatment.The ABO blood group system is a common example of multiple alleles in humans. This system includes three alleles called IA, IB, and i alleles, which combine in...
02:41
Lethal Alleles
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2021
Agouti: A Lethal Allele Lucien Cuénot discovered lethal alleles in 1905 while studying the inheritance of coat color in mice. The agouti gene is responsible for the color of the coat in mice. This gene codes for an agouti-signaling protein, which is responsible for melanin distribution in mammals. The wild-type allele gives rise to gray-brown coat color in mice, while the mutant allele gives rise to yellow coat color. In addition to coat color, the agouti gene is associated with the yellow...
FAQs
Sequencing depth determines how many reads support a measured proportion at a locus. A VAF calculated from limited coverage may be more vulnerable to the effect of individual reads, while deeper coverage supplies a larger read set for evaluating the same alternate-to-total relationship. Consequently, depth should accompany VAF interpretation rather than treating the fraction as independent of data quantity.
The measured fraction reflects the mixture of cells represented in the sequencing sample, not only the cells carrying the variant. If variant-bearing cells make up a smaller portion of the material, their reads can represent a smaller share of the total. Tumor purity therefore becomes important when interpreting VAF in samples containing both tumor and non-tumor cells.
Copy-number changes alter the genomic context in which a variant is measured. Because the alternate-allele proportion depends on the reads contributed by the relevant genomic copies, the same biological variant may produce different VAF patterns when copy number differs. VAF should therefore be interpreted alongside copy-number information rather than used alone to infer the abundance of variant-bearing cells.
First identify the alternate-allele read count and the total number of reads covering the genomic position, then calculate their ratio. Next, review sequencing depth, sample composition, tumor purity, copy-number changes, and possible technical errors. This workflow separates the numerical measurement from the biological interpretation and helps determine whether the observed value is informative for the study.
VAF patterns provide evidence about how broadly a variant is represented within a sample. A variant found across a larger population may show a different fraction from one restricted to a subclone, while mosaic variation reflects the presence of the variant in only some cells. These interpretations remain dependent on purity, copy number, depth, and technical reliability.
During variant calling, VAF helps describe how strongly sequencing data support a specific alternate allele at a genomic position. Comparing the fraction with read coverage and potential technical errors can also reveal whether an apparent signal is reliable or may reflect a problematic sample or measurement. Thus, VAF contributes both to identifying variants and to judging supporting data quality.
Repeated VAF measurements can show whether the representation of a variant changes across disease-related samples or during treatment monitoring. A rising or falling value may indicate a change in the population carrying that variant, although interpretation still requires attention to sample composition, tumor purity, copy-number changes, sequencing depth, and technical error.