Evolution

Sunny Days

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Science  11 Oct 2013:
Vol. 342, Issue 6155, pp. 163
DOI: 10.1126/science.342.6155.163-d

The human melanocortin-1 receptor (MC1R) locus in humans is involved in regulating melanin synthesis and hence skin pigmentation; some alleles are associated with lighter skin pigmentation, and several nonfunctional variants are associated with fair skin, red hair, and poor tanning capacity. Furthermore, light skin pigmentation is a risk factor for melanoma. Martínez-Cadenas et al. examined the genetic diversity of the MC1R locus in Spain and compared it to those of other populations. MC1R showed high levels of diversity that appear to be due to high CpG content, which are sites of mutation. However, despite the high level of observed mutation, the authors found evidence that most alleles are being removed from the population and are under purifying selection in Spaniards. One exception was the most common variant V60L, which appears to be under positive selection, although it showed spatial heterogeneity. Interestingly, V60L was also the most common variant in a sample of melanoma patients, suggesting that although it may be under positive selection, it has a deleterious and postreproductive consequence as well.

Mol. Biol. Evol. 30, 10.1093/molbev/mst158 (2013).

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