Originally Posted By: KazJaps
Just released Dec 2017 paper, includes research on Seramas, etc:

Wang et al., 2017. An Evolutionary Genomic Perspective on the Breeding of Dwarf Chickens.
Molecular Biology and Evolution, Volume 34, Issue 12, 1 December 2017, Pages 30813088, https://doi.org/10.1093/molbev/msx227
Abstract only
Herein, we explore the evolution of the Serama, the smallest breed of chicken. Leveraging comparative population genomics, analyses identify several genes that are potentially associated with the growth and development of bones and muscles. These genes, and in particular both POU1F1 and IGF1, are under strong positive selection. Three allopatric dwarf bantams (Serama, Yuanbao, and Daweishan) with different breeding-histories, form distinct clusters and exhibit unique population structures. Parallel genetic mechanisms underlay their variation in body size. These findings provide insights into the multiple and complex pathways, depending on genomic variation, that chicken can take in response to aviculture selection for dwarfism.

Full text is online