Are Bobtail Cats Born with Short Tails?
📝 Summary
Let's talk about bobtail cats. I once thought short tails were broken or docked — so sad — but later learned they're born that way, decided by genes.
1 Overview
The link between short tails and genes
A research team at Peking University studied the similarity between the short-tailed Japanese bobtail and the tail shape seen in cats from southern China.
Hypothesizing a shared genetic variant, they conducted a large-scale gene survey of cats by tail length.
First, they examined the Manx ‘T-box’ gene variants in 20 short-curly-tailed cats and 20 normal-tailed cats from southern China. No tail-deformity mutations were found.
The team crossbred a short-tailed female from southern China with a normal-tailed male; two litters produced 11 kittens. Observing tails: three normal, three mildly short, five moderately short.
From this pattern, short tail was confirmed as autosomal dominant, but with variation in length, so it’s also incomplete dominance (the dominant factor isn’t always 100% expressed).
Later, a large comparison of hundreds of normal- and short-tailed cats revealed the following.
The relationship between cat short tails and genes
HES7 on chromosome E1 is the causative gene for short tails
When T is replaced by C in HES7, tail deformation occurs
If the genotype is heterozygous C/T, mild to moderate short tail
When homozygous C/C, severe short tail
Short tails form from three changes: reduced caudal vertebrae, hemivertebrae, and fused vertebrae
HES7 is unrelated to body deformities other than tail and ribs
HES7 has no effect on fertility or survival
Even without the HES7 variant, some cats show short tails
Normal-tailed cats have no HES7 variant
Mutation in HES7 causes the short tails common in Southeast Asia and southern China.
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