Traditional chicken breeds exhibit a range of phenotypic diversity, which in some cases is far removed from that of their jungle fowl ancestors. This diversity includes plumage pattern and colouration, feather stlUcture, comb morphology, egg colour, and numerous other behavioural and morphological characteristics. Extensive research over the last century has identified that a number of these phenotypic traits are inherited in a Mendelian fashion, enabling them to be studied at the genetic level with relative ease. Typically, the genetic mapping of these traits has required establishing resource mapping populations through inter-crossing or back-crossing to select for the trait(s) of interest. However, recent advances in technology have demonstrated that it is possible to fine-map phenotypic traits by comparing the DNA of different breeds. Through the contrasting of single-nucleotide polymorphisms (SNPs) in a range of breeds exhibiting the trait of interest, to breeds in which the trait is absent, it is possible to take advantage of countless recombination events that have taken place since the different breeds were established, enabling the trait to be mapped at higher resolution than might be achieved through a resource mapping population.