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Review
. 2015 Sep;201(1):1-12.
doi: 10.1534/genetics.115.176750.

Genetic Diversity and Societally Important Disparities

Noah A Rosenberg  1 , Jonathan T L Kang  2
Affiliations
Review

Genetic Diversity and Societally Important Disparities

Noah A Rosenberg et al. Genetics. 2015 Sep.

Abstract

The magnitude of genetic diversity within human populations varies in a way that reflects the sequence of migrations by which people spread throughout the world. Beyond its use in human evolutionary genetics, worldwide variation in genetic diversity sometimes can interact with social processes to produce differences among populations in their relationship to modern societal problems. We review the consequences of genetic diversity differences in the settings of familial identification in forensic genetic testing, match probabilities in bone marrow transplantation, and representation in genome-wide association studies of disease. In each of these three cases, the contribution of genetic diversity to social differences follows from population-genetic principles. For a fourth setting that is not similarly grounded, we reanalyze with expanded genetic data a report that genetic diversity differences influence global patterns of human economic development, finding no support for the claim. The four examples describe a limit to the importance of genetic diversity for explaining societal differences while illustrating a distinction that certain biologically based scenarios do require consideration of genetic diversity for solving problems to which populations have been differentially predisposed by the unique history of human migrations.

Keywords: forensic DNA; genetic diversity; genome-wide association; human migration; transplantation matching.

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Figures

Figure 1
Figure 1
Expected heterozygosity as a measurement of diversity. Each axis in the unit square represents an allele frequency distribution, with each area representing the probability that an individual has a particular ordered pair of alleles. The shaded regions represent heterozygous combinations. The two loci shown represent different expected heterozygosity levels (equation 1). (A) A smaller heterozygosity (0.540). (B) A larger heterozygosity (0.725).
Figure 2
Figure 2
The serial founder model in human evolution. (A) A schematic of the model. Each color represents a distinct allele. Migration events outward from Africa tend to carry with them only a subset of the genetic diversity from the source population, and some alleles are lost during migration events. (B) An example of the model at a particular genetic locus, TGA012. Each set of vertical bars depicts the allele frequencies in a population, with different colors representing distinct alleles. Within continental regions, populations are plotted from left to right in decreasing order of expected heterozygosity at the locus [equation (3)]. This figure illustrates the loss of alleles across geographic regions; Native Americans all possess the same allele. The allele frequencies are taken from Rosenberg et al. (2005).
Figure 3
Figure 3
Familial identification in forensic testing. A contributor to a crime scene DNA sample has genotype AA at a locus. A sibling of the contributor is likely to share more alleles with the contributor than are unrelated individuals; the probability of an exact match at a locus, as shown, exceeds 25% for a sibling. This figure illustrates that in a low-diversity population, the chance of a false-positive match of an unrelated individual to a crime-scene contributor at a locus is greater than in a high-diversity population. In the low-diversity population, two nonrelatives have exact matches, and one has a partial match, whereas in the high-diversity population, the nonrelatives do not have exact or partial matches.
Figure 4
Figure 4
The principle of linkage disequilibrium that underlies genome-wide association studies. This figure depicts a series of individuals with a disease, tracing the genealogy of the section of the chromosome on which a disease-causing allele is located. A disease allele (orange) occurs on an ancestral chromosome containing several marker alleles (yellow, brown, red, and purple). Recombination events (arrows) break down correlations between the disease mutation and marker alleles, so the closer a marker allele is to the mutation, the more likely it is to be found in present-day disease cases.
Figure 5
Figure 5
The distribution across 1000 replicate subsamples of regression P-values for the influence of observed genetic diversity and its square on a proxy for economic development. Each panel represents a regression model (regressions 1, 4, or 5, as in Table 1 and Table S1, Table S2, and Table S3) and a variable whose significance is tested (observed diversity or its square). Each replicate subsample considers 21 countries. The red bar indicates the fraction of subsamples for which the P-value is smaller than 0.05.
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