Question

How is admixture mapping used to identify disease-associated loci in ethnicities/ancestral populations with differing degrees of disease susceptibly?

Answer 1

A population of mixed ancestry emerges due to the interbreeding of ancestrally different population who have remain reproductively isolated and genetically differentiated due to geographical isolation. Admixture mapping has gained importance over the years as a method of gene mapping for traits or diseases that show differential susceptibility and risk in different ancestry.

To start with, the ancestral genotype data of the ancestral and the admixed population are required. Different markers that differ largely among populations are called Ancestral Informative Marker (AIM) and they are assigned in order to differentiate one population from another. The two most widely used AIM were delta and F_ST. Delta is the difference in allele frequencies among two different population. F_ST is the ratio of variance of allele frequencies and the variance of allele frequencies in the absence of population structure. Number of these markers increase with the number of generations of the admixed population. These markers are used for association studies between a disease and susceptibility loci. Phenotypes of a particular disease vary between the populations. Whether this difference stems solely for genotype difference or occurs due to perturbation by environmental factors is a big question. Admixture mapping using the data from genome wide microarrays , whole genome sequencing etc. can infer the differential risk of a disease in admixed population.

Reference :

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3556814/pdf/nihms435998.pdf

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3146309/pdf/nihms311911.pdf

PS : Please contact in the comment section in case of any confusion and don't forget to rate. TIA