Manx cat
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.