Minor allele frequency (MAF) is the frequency at which the ''second most common''
allele occurs in a given population. They play a surprising role in
heritability
Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of ''variation'' in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of h ...
since MAF variants which occur only once, known as "singletons", drive an enormous amount of selection.
Single nucleotide polymorphism
In genetics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in a sufficiently larg ...
s (SNPs) with a minor allele frequency of 0.05 (5%) or greater were targeted by the
HapMap project.
MAF is widely used in
population genetics studies because it provides information to differentiate between common and rare variants in the population.
As an example, a 2015 study sequenced the whole
genomes of
Sardinian individuals. The authors classified the variants found in the study in three classes according to their MAF. It was observed that rare variants (MAF < 0.05) appeared more frequently in coding regions than common variants (MAF > 0.05) in this population.
Interpreting MAF data
1. Introduce the reference of a SNP of interest, as an example:
rs429358
Apolipoprotein E (APOE) is a protein involved in the metabolism of fats in the body of mammals. A subtype is implicated in Alzheimer's disease and cardiovascular disease.
APOE belongs to a family of fat-binding proteins called apolipoproteins. ...
, in a database (dbSNP or other).
2. Find MAF/MinorAlleleCount link. MAF/MinorAlleleCount: C=0.1506/754 (1000 Genomes, where number of genomes sampled = N = 2504);
National Center for Biotechnology Information: ''New SNP Attributes''
/ref> where C is the minor allele for that particular locus; 0.1506 is the frequency of the C allele (MAF), i.e. 15% within the 1000 Genomes database; and 754 is the number of times this SNP has been observed in the population of the study.
See also
* Allele frequency
References
Classical genetics
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