Inheritance of White Colour in Alpacas - Australian Alpaca Association

Tyrp1 produces an enzyme that acts in the melanin synthesis pathway (Figure 1.3) and is known
colloquially as the “brown” locus. A mutated Tyrp1 causes brown eumelanin instead of black. The
recessive brown variant of Tyrp1 is found in dogs and mice, but does not exist in horses. It is possible
that no brown alleles exist in alpacas because breeding outcomes suggest that brown in alpacas is
dominant, rather than recessive. It is also possible that the same phenotype (i.e. brown) can be caused
by two different mechanisms in alpacas and that that both recessive brown and dominant brown
(probably occurring at the agouti locus) exist.
Figure 1.6: Comparisons of colour and pattern in different species.
Two other genes, tyrosinase (Tyr) and membrane associated transporter protein (Matp), may also be
involved in colour variation in alpacas. Tyr is the gene that produces the enzyme tyrosinase, which is
the key enzyme in the melanogenesis pathway (Figure 1.3). In species such as mice, rabbits and cats,
variants of Tyr are known to produce a dilution of colour, including albinism (Lamoreux et al. 2010).
Matp is the gene that is mutated in palomino and buckskin horses (Mariat et al. 2003). It has been
hypothesised that some white alpacas are the equivalent of cremello horses. That is, they are chestnut
with two doses of the dilution gene causing a massive reduction in the intensity of colour so that they
appear white.
The following genes are hypothesized to have multiple variants in alpacas, and thereby cause colour
variation: Agouti (A), Mc1r (E), Roan (Rn), Grey (M), Tuxedo (T), Piebald (P), Appaloosa. These
genes can be broken into two groups, those that affect the base colour of the animal (Mc1r and Agouti)
and those that cause alterations to the base colour (grey, roan, tuxedo, piebald and appaloosa). Other
genes are almost certainly affecting colour, but these have not yet been identified, e.g. the gene(s) that
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