The chocolate plumage color in chickens is due to a sex‐linked recessive mutation, choc, which dilutes eumelanin pigmentation. Because TYRP1 is sex‐linked in chickens, and TYRP1 mutations determine brown coat color in mammals, TYRP1 appeared as the obvious candidate gene for the choc mutation. By combining gene mapping with gene capture, a complete association was identified between the chocolate phenotype and a missense mutation leading to a His214Asn change in the ZnA zinc‐binding domain of the protein. A diagnostic test confirmed complete association by screening 428 non‐chocolate chickens of various origins. This is the first TYRP1 mutation described in the chicken. Electron microscopy analysis showed that melanosomes were more numerous in feather follicles of chocolate chickens but exhibited an abnormal structure characterized by a granular content and an irregular shape. A similar altered morphology was observed on melanosomes of another TYRP1 mutant in birds, the roux mutation of the quail.

中文翻译：

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TYRP1的错义突变会导致鸡肉中的巧克力羽毛颜色变色，并改变黑素体的结构

鸡体内的巧克力羽毛颜色是由于性相关的隐性突变choc所致，它稀释了Eumelanin的色素沉着。因为TYRP1在鸡中是性别相关的，并且TYRP1突变决定了哺乳动物的棕色被毛颜色，所以TYRP1似乎是choc突变的明显候选基因。通过将基因定位与基因捕获相结合，可以确定巧克力表型与错义突变之间的完全关联，该错义突变导致蛋白质的ZnA锌结合域中的His214Asn发生变化。诊断测试通过筛查428种不同来源的非巧克力鸡来确认完全相关。这是第一个TYRP1鸡中描述的突变。电子显微镜分析表明，巧克力鸡的羽毛卵泡中的黑素体数量较多，但表现出异常结构，其特征在于颗粒含量和不规则形状。在鸟类的另一种TYRP1突变体（鹌鹑的肉汁突变）的黑素体上观察到了类似的形态变化。