An ancestry-informative marker
(AIM) is a set of polymorphisms for a locus, generally from humans, which exhibits substantially different frequencies between populations from different geographical regions. For example, the Duffy
Null allele (FY*0) has a frequency of almost 100% of Sub-Saharan Africans, but occurs very infrequently in populations outside of this region. A person having this gene is thus more likely to have Sub-Saharan African ancestors. By using a number of AIMs one can estimate the geographical origins of the ancestors of an individual and ascertain what proportion of ancestry is derived from each geographical region. By using a suite of these markers more or less evenly spaced across the genome, they can be used in a cost-effective way to discover novel genes underlying complex diseases in a technique called admixture mapping or mapping by admixture linkage disequilibrium. A collection of AIMs that distinguish African and European populations contains 3011 highly differentiated SNP
's. While this may seem like a large number to someone not familiar with genomics
, it is important to note there are an estimated 35,000,000 SNP sites with greater than 1% allelic frequency in the Human Genome
. Other collections of AIMs have been developed that can estimate the geographical origins of ancestors from within Europe. This has been developed into a commercial package.
Charles Rotimi, of Howard University's National Human Genome Center, is among those who have highlighted the methodological flaws in such research — that "the nature or appearance of genetic clustering (grouping) of people is a function of how populations are sampled, of how criteria for boundaries between clusters are set, and of the level of resolution used" all bias the results — and concluded that people should be very cautious about relating genetic lineages or clusters to their own sense of identity. (see also How much are genes shared? Clustering analyses and what they tell us)
The company DNAPrint Genomics sells a kit for police to use to identify the ancestry of criminals based on DNA samples from them.
- Shriver, Mark D. et al., "Skin pigmentation, biogeographical ancestry and admixture mapping," Hum. Genet. 112, 387-399 (2003)
- SNP Science Primer
- dbSNP Summary
- Explanation from DNAPrint Genomics