Dominant Blue Eye Register

The Global Cat Health Survey's dominant blue eye register

Blue eyes in cats are usually the work of the colorpoint gene or of white markings. In a small number of families, they are not. A separate, dominant determinant is the inheritance of these lines, and at least four such variants have now been identified, all in the same gene, PAX3.

The directory at blueeyesdirectory.com is an attempt to write those families down before the paperwork is lost. It holds 4,365 records across 56 breeds and 133 countries, assembled from registry pedigrees, breeder charts, certificates, and the breeders' own accounts. Every claim carries its source and its grade of evidence, and a line label is never confused with a traced descent.

The register exists for one question in particular. A cat inheriting one determinant from each parent is a compound heterozygote, and that is the state in which harm is documented in this trait: white coats, deafness, and, in some lines, the loss of homozygous kittens before birth. The directory names that class directly.

Every cat in the register now has its own variant trace certificate. One page per animal, giving what the register holds, which founders stand above it and by what chain of parents, and a plain statement of what the trace does not establish. Where a photograph has been supplied, it appears on the certificate, with the cat between its sire and its dam, and each picture carrying its own credit. It saves to PDF from any browser, so it can travel with a pedigree or go to a vet.