In other species: cattle , horse , dog , sheep , pig , golden hamster , North American deer mouse , goat , American mink , rabbit , Mongolian gerbil

Possibly relevant human trait(s) and/or gene(s)s (MIM numbers): 612271 , 203290

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal

Considered a defect: no

Key variant known: yes

Year key variant first reported: 2005

Inheritance: As summarised by Lyons et al. (2005), "Brown, B, has a suggested allelic series, B > b > b1. The B allele is normal wild-type black coloration. Cats with the brown variation genotypes, bb or bb1, are supposedly phenotypically chocolate (aka chestnut) and the light brown genotype, b1b1, are supposedly phenotypically cinnamon (aka red)."

Molecular basis: By sequencing a very likely comparative candidate gene (based on the homologous traits in other mammals), Lyons et al. (2005) uncovered the molecular basis for several phenotypes at this locus in cats. The relevant gene is tyrosinase-related protein-1 (TYRP1). Specifically, they showed: "The C to T nonsense mutation at position 298 causes an arginine at amino acid 100 to be replaced by the opal (UGA) stop codon. This mutation is consistent with the cinnamon phenotype and is the putative light brown, b1, mutation. An intron 6 mutation that potentially disrupts the exon 6 downstream splice-donor recognition site is associated with the chocolate phenotype and is the putative brown, b, mutation." One month later, Schmidt-Küntzel et al. (2005) independently reported the same results.

Associated gene: