Why the Bengal cat can be black?
The "a" allele represents the non-agouti form of the gene that affects the coat color in cats. In a melanistic Bengal cat, the presence of the "a" allele affects the distribution of pigments in the fur. When a Bengal cat carries two copies of the "a" allele (genotype aa), it suppresses the agouti signaling and allows the production of eumelanin (black pigment) to be more evenly distributed across the coat, resulting in a darker and more uniform black coloration. This is what gives a melanistic Bengal cat its black coat coloration.