Mendelian trait/disorder: yes

Mode of inheritance: Autosomal Recessive

Considered a defect: no

Key variant known: yes

Year key variant first reported: 2014

Species-specific symbol: mo

Species-specific description: As described by Somes (1980), this trait is characterised by "a white tip on an otherwise black feather".

History: This trait was first described in the genetics literature by Davenport (1906).

Inheritance: Davenport (1906) reported autosomal recessive inheritance. This was confirmed by Asmundson and Milne (1930). The symbol "mo" was proposed by Hutt (1949). Somes (1980) also confirmed autosomal recessive inheritance. Carefoot (1987) reported "that pi [pied] and mo are one and the same gene for which I retain the symbol mo". A new allele at this locus, conferring white plumage with black eyes in the Minohiki breed (from Japan), was reported by Kinoshita et al. (2014), who allocated it the symbol mo^w, with the name tyrosine-independent recessive white.

Molecular basis: Adopting a comparative-candidate-gene strategy, based on a mutation in the gene EDNRB2 being causal for a similar phenotype (panda) in Japanese quail (OMIA 000375-93934), and on the appearance of an F1 hybrid between a panda (s/s) quail and a mo^w/mo^w chicken, Kinoshita et al. (2014) identified "a non-synonymous G1008T substitution, which causes Cys244Phe amino acid substitution in exon 5 (which is part of the extracellular loop between the putative fourth and fifth transmembrane domains of EDNRB2) in the mutant [mo^w] chicken. This Cys244Phe mutation was also present in individuals of four Japanese breeds with white plumage. We also identified a non-synonymous substitution [G1272A] leading to Arg332His substitution that was responsible for the mottled (mo/mo) plumage phenotype."

Breed: Minohiki.

Associated gene: