Cat body-type mutation

Cats, like all living organisms, occasionally have mutations that affect their body type. Sometimes, these cat body-type mutations are striking enough that humans select for and perpetuate them. This is not always in the best interests of the cat, as many of these mutations are harmful; some are even lethal in their homozygous form.

This page gives a selection of cat body type mutant alleles and the associated mutations with a brief description.

Jb = Japanese bobtail gene (autosomal dominant). Cats homozygous and heterozygous for this gene display shortened and kinked tails. Cats homozygous for the gene tend to have shorter more kinked tails. This can be distinguished phenotypically from the Manx cat mutation by the presence of kinking in the tail, often forming what looks like a knot at the distal end of the tail. Unlike the Manx tailless gene, there are no associated skeletal disorders and the gene is not associated with lethality.

M = Manx tailless gene (dominant with high penetrance). Cats with the homozygous genotype (MM) die before birth, and stillborn kittens show gross abnormalities of the central nervous system. Cats with the heterozygous genotype (Mm) show severely shortened tail length, ranging from taillessness to a partial, stumpy tail. Some Manx cats die before 12 months old and exhibit skeletal and organ defects. Because it was discovered in naturally occurring populations of cats, the Manx gene could confer some kind of selective advantage to the cats, or it may simply be an example of the founder effect. The trait also occurred and died out in Cornwall (peninsular England), but persisted in the Isle of Man population where outbreeding was not frequent due to isolation.

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