Ancestry-informative marker

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An ancestry-informative marker (AIM) is a gene, generally of humans, which has several polymorphisms that exhibit substantially different frequencies between groups of descendants derived from mutually inbred ancestral groups (often referred to as races by some sources). For example, the Duffy Null allele (FY*0) has a frequency of almost 100% of Sub-Saharan Africans, but occurs very infrequently in other races. A person having this gene is thus very likely to have some Sub-Saharan African ancestors. By using a number of AIMs one can estimate the ancestral (racial) proportion of an individual, as well as confidence intervals of the estimates. 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. [1]. While this may seem like a large number to someone not familair with genomics or genetics, it is important to note there are an estimated 35,000,000 SNP sites with greater than 1% allelic frequency in the Human Genome.

The company DNAPrint Genomics sells a kit for police to use to identify the ancestry of criminals based on DNA samples from them.

[edit] References

Shriver, Mark D. et al., "Skin pigmentation, biogeographical ancestry and admixture mapping," Hum. Genet. 112, 387-399 (2003)[2]
SNP Science Primer [3]
dbSNP Summary [4]
Explanation from DNAPrint Genomics