User:Holdenhansli/New sandbox

copied from Agouti (gene)

The agouti gene encodes the agouti-signaling protein (ASIP), responsible for the distribution of melanin pigment in mammals. Agouti interacts with the melanocortin 1 receptor to determine whether the melanocyte (pigment cell) produces phaeomelanin (producing a yellow to red hue) or the eumelanin (producing a brown to black hue). This interaction is responsible for making distinct light and dark bands in the hairs of animals such as the agouti. In other species such as horses, it determines what parts of the body are red or black.

The agouti-signaling protein (ASIP) competes with alpha-Melanocyte-stimulating hormone (α-MSH) to bind with melanocortin 1 receptor (MC1R) proteins. Activation by α-MSH causes production of the darker eumelanin, while activation by ASIP causes production of the redder phaeomelanin.

In mice, the wild type agouti allele (A) presents a grey phenotype, however, many allele variants have been identified through genetic analyses, which result in a wide range of phenotypes distinct from the typical grey coat. The most widely studied allele variants are the lethal yellow mutation (Ay) and the viable yellow mutation (Avy) which are caused by ectopic expression of agouti. The lethal yellow mutation occurs when there are two copies of the agouti allele, organisms with this combination will not survive until birth. The viable yellow mutation is interesting because it causes the organism to have a yellow coat, which is the recessive phenotype. These mutations are synonymous with the yellow obese syndrome which is characterized by early onset obesity, hyperinsulinemia and tumorigenesis.