The success of many strategies for finding genetic variants that underlie complex traits depends on how genetic variation is distributed among human populations. This realization has intensified the investigation of genetic differences among groups, which are often defined by commonly used racial labels. Some scientists argue that race is an adequate proxy of ancestry, whereas others claim that race belies how genetic variation is apportioned. Resolving this controversy depends on understanding the complicated relationship between race, ancestry and the demographic history of humans. Recent discoveries are helping us to deconstruct this relationship, and provide better guidance to scientists and policy makers.
Highlighting genetic differences among people could unfortunately reinforce stereotypical features of populations, but exploring the genetic influence on common health-related traits and disparities could also be beneficial to human health.
Accurate inference of an individual's ancestry using genetic data depends on several factors, including the number of genotypes used, the degree of differentiation among groups and how each group is sampled.
Inferences of human population structure based on genetic data often differ from inferences based on phenotypic characteristics.
Although there might be little variation among groups, it is highly structured and therefore useful for distinguishing groups and allocating individuals into groups.
Insofar as geographical ancestry corresponds to some notions of race, patterns of genetic variation will also co-vary with these notions.
The inaccurate measure of ancestry afforded by proxies of genetic relationships such as race or ethnicity can sometimes be useful, but in other circumstances, might lower the chances of findings disease-susceptibility loci and lessen the predictive value of clinical inferences.
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We thank S. Guthery and M. Pungliya for technical assistance, T. Frudakis for access to data from DNAPrint Genomics, S. Olson and L. Jorde for discussion, and four anonymous reviewers for comments and criticisms. M.B. and S.W. are supported by the US National Institutes of Health and the National Science Foundation.
supplementary information S1 (data)100 Alu insertion polymorphisms in Africans, Asians and EuropeansFile name: Bamshad_continental_alu_100.txt Refers to figures: 1a,1b,3a Column 1: Af, African; Eu, European; As, Asian. Column 2: continent code. Columns 3–103: Alu genotypes: 0, absent; 1, present. The genotype of each individual occupies 2 lines of text. Missing data indicated by ‘-9’.
supplementary information S4 (data)377 STRs typed in 1,066 individuals from CEPH diversity panel File name: Rosenberg_ceph_subset_str.txt Refers to figure: 2 Column 1: continent ID (Af, African; Eu, European; As, Asian) and individual ID. Genotypes scored by allele size and alleles at each locus are separated by a ‘.’. Missing data indicated by ‘?’.
supplementary information S5 (data)60 STRs typed in Africans, Asians and Europeans File name: Bamshad_continental_str_60.txt Refers to figure: 3b Column 1: Af, African; Eu, European; As, Asian. Column 2: continent code. Columns 3–63: STR genotypes scored by relative size of allele. The genotype of each individual occupies 2 lines of text. Missing data indicated by ‘-9’.
- POPULATION STRUCTURE
Organization of a population into sub-populations as a consequence of factors such as finite population size and geographical subdivision.
- FOUNDER POPULATION
A group of individuals that establishes a new population.
- ASSORTATIVE MATING
Nonrandom choice of mates based on phenotypic characteristics such as geographical proximity, skin colour, height or religion.
- GENETIC DRIFT
Fluctuations of allele frequencies over time due to chance alone.
A statistic that quantifies the dispersion of data about the mean.
A gradient in the frequency of an allele.
The mixing of two or more genetically differentiated populations.
- QUANTITATIVE TRAIT
A measurable trait that depends on the cumulative action of many genes and that can vary among individuals over a given range to produce a continuous distribution of phenotypes. Common examples include height, weight and blood pressure.
- LOCAL POSITIVE SELECTION
A type of natural selection in which favoured variants increase in frequency in a localized geographical region.
- DUFFY BLOOD GROUP
This group is defined by variants in a chemokine receptor that is present on the surface of several types of cell, including red blood cells. This receptor must be present for Plasmodium vivax to invade cells and cause malaria.
- CONVERGENT EVOLUTION
A process in which traits evolve to a similar state in two or more genetically distinct populations, typically as an adaptive response.
- BALANCING SELECTION
A selection regime that results in the maintenance of two or more alleles at a single locus in a population.
- CEPH HUMAN DIVERSITY PANEL
A resource of 1,064 cultured lymphoblastoid cell lines from individuals in 51 different world populations that are banked at the Foundation Jean Dausset (CEPH) in Paris, France.
A statistic similar to FST that is used to estimate differentiation among groups by using microsatellite markers.
The selection of samples (such as markers, individuals, populations) through a process that often deviates from random sampling and can therefore introduce bias.
The combination of alleles or genetic markers that is found on a single chromosome of a given individual.
An autosomal recessive condition that is common in Western Europeans and their descendants. It is characterized by excessive iron absorption by the gut, with subsequent accumulation in the liver, heart, joints and pancreas.
- CYSTIC FIBROSIS
An autosomal recessive condition that is common in Western Europeans and their descendants. It is characterized by pancreatic insufficiency and obstruction of the lungs by thick, heavy mucus.
The proportion of individuals with a specific genotype who manifest this genotype at the phenotype level.
- COMPLEX TRAIT
A trait that is influenced by the environment plus a combination of polymorphisms in at least several genes, each of which has a small effect.
- ADMIXTURE MAPPING
A strategy for mapping loci for complex traits that differ in prevalence between two populations that have recently admixed with each other.
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Journal of Cancer Research and Clinical Oncology (2015)