Description:
The crested gene creates a "poof" of feathers from the top of the skull in chickens. It is most commonly seen in Sultans, Polish, Houdans, and Silkies, though the shape of the crests vary wildly from breed to breed. This is due to the feather length, width, and shape that changes by breed. This gene is believed to be one of the oldest mutations in chickens, with evidence of crested chickens being studied as early back as ancient Rome (1).
Generally, the heterozygous forms of crested have smaller shaped crests, while the homozygous form has larger and more developed crests. Males will often have more prominent crests than females in both forms. This is because the
The homozygous form of crest has also been linked to malformed skulls and head-shapes, though it is uncertain whether a second, linked gene is responsible for this or if it is due to the crested gene itself (1) (2).
The APA recognizes Silkies, Sultans, Polish, Houdans, and Crevecoeur chickens to have crests. All other breeds should not have the crested gene in chickens.
Breeding with Crested:
Full crested x full crested = 100% full crested
Full crested x no crest = 100% het. crested
Full crested x het. crest = 50% het. crest, 50% full crest.
Het. crest x het. crest = 25% no crest, 50% het. crest, 25% full crest.
Het. crest x no crest = 50% het. crest, 50% no crest
References & Further Reading
Jingyi Li, Mi-Ok Lee, Brian W Davis, Ping Wu, Shu-Man Hsieh Li, Cheng-Ming Chuong, Leif Andersson, The crest phenotype in domestic chicken is caused by a 195 bp duplication in the intron of HOXC10, G3 Genes|Genomes|Genetics, Volume 11, Issue 2, February 2021, jkaa048, https://doi.org/10.1093/g3journal/jkaa048
Tsai DY, Chen JJ, Su PC, Liu IM, Yeh SH, Chen CK, Cheng HC, Chen CF, Li WH, Ng CS. Chicken HOXC8 and HOXC10 genes may play a role in the altered skull morphology associated with the Crest phenotype. J Exp Zool B Mol Dev Evol. 2023 Sep;340(6):392-402. doi: 10.1002/jez.b.23194. Epub 2023 Apr 11. PMID: 37039065.