Selkirk Rex vs Devon Rex vs Cornish Rex: Three Curls, Three Genetic Stories

One sentence beats every generalist curly-cat roundup, and it is checkable: three rex breeds, three different genes or alleles, and calling any two of them "the same mutation" is wrong. Here is the precise version, from the four genetics papers our research read in full. Plus the population finding that explains why the Selkirk's health file belongs to a family you would not guess.

The three curls, precisely

The Selkirk Rex curls by a DOMINANT mutation (the SADRE allele) in KRT71, the hair-keratin gene: one copy curls the cat. The Devon Rex curls by a RECESSIVE mutation (re) in the SAME gene at a different site: two copies required. The same gene also hosts the Sphynx's hairlessness allele, with a strict pecking order between them. The Cornish Rex is the outsider.

Its marcel wave comes from a mutation in a COMPLETELY different gene, LPAR6 (called P2RY5 in older papers: two names, one gene, worth saying once so older sources don't confuse you). Even within KRT71, the Selkirk's mutation sits at a different splice site than the Devon's (an acceptor rather than a donor site), producing a much smaller molecular change. Same gene, different break, different inheritance.

What dominance changes in practice

The Selkirk's dominant curl is why its litters mix curly and straight kittens, why straight Selkirks are real registrable members of the breed, and why heterozygous (one-copy) cats are the favored breeding cats per GCCF's own Breeding Policy. Pairing choices genuinely differ by genotype, and one US cattery even prices kittens by it. The Devon and Cornish, both recessive, breed true curly-to-curly: no straight surprises, no genotype ladder.

The finding nobody expects: the Selkirk is a Persian-family cat

The population-genetics paper our research read in full (Filler et al. 2012) clusters the Selkirk Rex genetically with the British Shorthair, Scottish Fold, Persian and Exotic Shorthair: in its own words, part of the Persian breed family. Two registry documents point at the same family through a different mechanism.

GCCF's Breeding Policy and Canada's standard both route Selkirk breeders to the British Shorthair's own color-genetics documentation. The practical consequence is the breed's whole health frame. Selkirks are screened for PKD and HCM not because the breed has been measured to carry them, but because its outcross family demonstrably does. The Devon and Cornish, whippet-built southwest-England natives, share none of that file.

Telling the three apart in a room

The Selkirk: a round, heavy-boned, teddy-bear cat (its Persian-family build) in loose, plush, tousled curls, long or short. The Devon: a pixie face, huge low-set ears, and a loose, delicate wave on a light frame. The Cornish: the greyhound of the three, all arches and marcel waves with no guard hairs at all. Round-and-plush, elfin-and-wavy, racy-and-rippled: once you hold the three frames, the curls stop confusing.