Understanding Selkirk Rex genetics
- Alexandra
- Nov 18
- 4 min read
One of the questions we are asked, is also one of the most fascinating: Where do those amazing curls of a Selkirk Rex come from? When we first started looking into Selkirks, to decide whether to pursue importing and breeding - we learned immediately, they are not as straight forward as other curly cats who were built on a foundation of recessive genetic mutation.
The plush, curly coat of the Selkirk Rex is a fascinating story of genetics, a happy accident, and super cool science. Unlike other rex breeds, the Selkirk coat is the result of a unique, dominant gene.
For anyone who loves the breed or is considering welcoming a Selkirk into their home, understanding the science behind the coat is a fascinating peek into what makes these cats so special. Thanks to two key scientific studies (Filler et al., 2012 and Gandolfi et al., 2013), we can pull back the curtain on Selkirk Rex genetics.
The Origin of the Breed
The entire Selkirk Rex breed began with one spontaneous mutation. In 1987, a shelter cat in Montana, USA, gave birth to a litter that included one very unusual, curly-coated female kitten. This kitten was named Miss DiPesto, and eventually bred to a Persian male, and her resulting litter contained both curly-haired and straight-haired kittens.
This first mating immediately told researchers something crucial: the curly gene had to be autosomal dominant.
Autosomal means it's not linked to sex (both males and females can inherit and pass it on).
Dominant means you only need one copy of the gene to show the trait.
This original cat was the foundation of the entire breed, which is why the Selkirk Rex is the most recent rex mutation to be developed into an internationally recognized breed.
An "Incomplete" Dominant Gene
Here's where the genetics get really interesting for breeders and enthusiasts. Further research into the breed's inheritance patterns confirmed that the gene is not just dominant, but incomplete dominant.
This means there are three possible genetic combinations, each with a distinct look:
Straight-Haired (No curl gene): This is a Selkirk Rex that did not inherit the curl gene from its parents. They have a straight coat, just like any other cat.
Heterozygous (One copy of the curl gene): This is the desired, breed-standard look. These cats have the full, plush, randomly curled coat that the breed is famous for.
Homozygous (Two copies of the curl gene): These cats can be distinguished from the others. They tend to have a tighter, softer, wavier curl that is less random and can look more like a Cornish Rex's coat. They may also have a more slender body and larger ears, which is not the desired head type for the breed. Homozygous kittens may also lose their coat when they are young.
Because the heterozygous cats exhibit the ideal coat and head type, they are what responsible breeders aim for in their programs. What this also means, is that offspring from heterozygous cats may produce either straight haired or homozygous kittens.
Scientists Find the Exact Gene
For years, breeders knew the trait was dominant, but the specific gene was a mystery. In 2013, a study by Gandolfi et al. finally "cracked the code."
Using a genome-wide association study (GWAS), scientists compared the DNA of curly Selkirk Rex cats against straight-haired Selkirks, Persians, and British Shorthairs. They found a single, powerful genetic signal on cat chromosome B4.
They pinpointed the exact gene: KRT71 (Keratin 71).
Keratin is a protein that gives hair its structure and rigidity. The mutation in Selkirk Rex cats is a specific "splice variant," which means the genetic instructions are read in a slightly different way. This change ultimately causes a small piece of the KRT71 protein to be left out, disrupting the hair's normal structure and causing it to curl.
How Selkirks Compare to Other Breeds
Here’s one of the most fascinating takeaways from the scientific research. The Selkirk Rex isn't the only curly cat, but its mutation is unique.
vs. Devon Rex & Sphynx: Amazingly, these breeds also have mutations in the same KRT71 gene. However, their mutations are recessive (meaning they need two copies) and are in different locations on the gene, which is why they have a completely different hair type.
vs. Cornish Rex: The Cornish Rex's curls are caused by a mutation on a completely different gene (P2RY5).
This means the Selkirk Rex's dominant KRT71 mutation is genetically distinct and not found in any other rex or hairless breeds.
A Diverse and Healthy Foundation
What does all this mean for the breed today? The history of the Selkirk Rex, starting from that one shelter cat and including outcrosses to breeds like Persians and British Shorthairs, is a huge advantage.
These outcrosses have resulted in a breed with a high level of genetic diversity. This is fantastic news, as it provides a wide, healthy genetic foundation for the breed's future. It also means there is a huge variation in what we can choose to breed for, the goal of reaching good 'per-standard' conformation can shift each generation, we can play a long game - and introduce both British longhair and shorthaired, and Persian or Exotic cats into the programme to improve features.
Here at Apokalypt, understanding this science is a core part of our mission. We are familiar with environmental science and biology, so this was the ultimate appeal with Selkirks. We can make responsible, informed breeding decisions that honour the breed's unique history, protect its health, and produce beautiful, curly kittens that are the hallmark of the Selkirk Rex.
References
Filler, S., Alhaddad, H., Gandolfi, B., Kurushima, J.D., Cortes, A., Veit, C., Lyons, L.A., & Brem, G. (2012). Selkirk Rex: Morphological and Genetic Characterization of a New Cat Breed. Journal of Heredity, 103(5), 727–733. doi: 10.1093/jhered/ess039
Gandolfi, B., Alhaddad, H., Joslin, S.E.K., Khan, R., Filler, S., Brem, G. & Lyons, L.A. (2013). A splice variant in KRT71 is associated with curly coat phenotype of Selkirk Rex cats. Scientific Reports, 3, 2000. doi: 10.1038/srep02000
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