Oculocutaneous Albinism Type I (TYR gene, Siamese)
Specific alterations in the TYR gene, which regulates melanin production, can cause reduced pigmentation in areas of the body. These changes are also associated with oculocutaneous albinism type I.
Definition
Type I oculocutaneous albinism in the Siamese breed is related to the TYR gene, which encodes the enzyme tyrosinase, essential for melanin production. In Siamese cats, tyrosinase is temperature sensitive, functioning better in cooler parts of the body and producing more melanin in these areas (ears, face, paws and tail). In warmer areas, the activity of the enzyme decreases, resulting in a lighter coat.
Genetic basis
The C locus in the TYR gene determines coat coloration. At this locus there is the following allelic series: C > c^b = c^s > c, c^2. The C allele corresponds to the wild-type allele that produces melanin. In this case, we analyzed the c^s allele which causes a characteristic "dotted" coloration pattern due to the c. 904G>A substitution in the TYR gene. This trait is inherited in an autosomal recessive manner, meaning that it requires the presence of two copies of the genetic variant for expression of the phenotype. Cats that have only one copy of this variant will not show the trait, but can transmit the allele to their offspring with a 50% probability.
Other relevant information
Other alleles of the same C locus are associated with other characteristic coats: the C allele allows normal melanin production, the c allele causes complete absence of coloration, while the c^b (Burmese cat) and c^s (Siamese cats) alleles reduce melanin production, creating specific color patterns. Although the TYR gene is related to oculocutaneous albinism, in this case this mutation does not cause complete albinism but hypopigmentation.
Do you still not know the true nature of your cat?
Unlock the secrets of your pet's DNA with our two ranges.
