A sexual ornament in chickens is affected by pleiotropic alleles at HAO1 and BMP2, selected during domestication

PLoS Genet. 2012;8(8):e1002914. doi: 10.1371/journal.pgen.1002914. Epub 2012 Aug 30.


Domestication is one of the strongest forms of short-term, directional selection. Although selection is typically only exerted on one or a few target traits, domestication can lead to numerous changes in many seemingly unrelated phenotypes. It is unknown whether such correlated responses are due to pleiotropy or linkage between separate genetic architectures. Using three separate intercrosses between wild and domestic chickens, a locus affecting comb mass (a sexual ornament in the chicken) and several fitness traits (primarily medullary bone allocation and fecundity) was identified. This locus contains two tightly-linked genes, BMP2 and HAO1, which together produce the range of pleiotropic effects seen. This study demonstrates the importance of pleiotropy (or extremely close linkage) in domestication. The nature of this pleiotropy also provides insights into how this sexual ornament could be maintained in wild populations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alcohol Oxidoreductases / genetics*
  • Alleles
  • Animals
  • Bone Morphogenetic Protein 2 / genetics*
  • Chickens / genetics*
  • Comb and Wattles* / anatomy & histology
  • Comb and Wattles* / growth & development
  • Crosses, Genetic
  • Fertility / genetics
  • Genetic Linkage
  • Genetic Pleiotropy*
  • Male
  • Phenotype
  • Quantitative Trait Loci
  • Selection, Genetic


  • Bone Morphogenetic Protein 2
  • Alcohol Oxidoreductases
  • HAO1 protein, human
  • glycollate oxidase

Grant support

This study was funded by the Foundation for Strategic Environmental Research and the Swedish Research Council for Environmental, Agricultural Sciences, and Spatial Planning. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.