Although
the fold-ear cat was first bred in Scotland in 1964, there was no mention
of associated skeletal deformity until the seventies, but by 1971 several
"skeletally abnormal" cats were alive and the condition was recognized
by a number of people.
A preliminary genetic study of fold-ear cats has
been made by Dyte and Turner (1973), but in view of the severe skeletal
abnormality identified by 1971, further breeding was undertaken by Oliphant
F. Jackson to identify the developmental nature of the skeletal lesions.
Histological examination of bones from skeletally
affected kittens showed that the site of defective bone growth was at
the level of the growth plates (epiphyseal cartilages) and in the adjacent
metaphyses. In the growth plates the proliferation of chondrobalsts
was disordered with irregular groups of cells arranged in haphazard
fashion. The epiphyseal plates were grossly expanded with deficient
ossification, irregular mineralisation and defective remodeling. Supernumerary
centers of ossification were found in all affected epiphyses.
To an observant person the skeletally affected
cats have not only short thick inflexible tails but gross deformity
of the limb extremities with limb dysfunction, reduced ability to support
the body weight, and overgrowth of nails, which may grow round and penetrate
the pads and, in consequence, greatly reduced activity.
The breeding records of the three controlled methods
of breeding suggested that the gene for fold-ears was a simple dominant
gene with complete penetrance. It is to be hoped that strict control
will be maintained to ensure that fold-ear is never mated to fold-ear.
Since the gene (Fd) is a simple dominant, it
will be all too easy to produce numerous fold-ear cats by breeding fold-ear
to a normal straight-ear cat and yet not produce any skeletal abnormality.
If the potential of putting a cat at risk for
a lifetime of discomfort and pain were not sufficient cause to avoid
Fold-to-Fold mating, the lack of profit from this dangerous investment
would be. Unions between two Fold-ear cats produce three Fold kittens,
on average, out of every four kittens born. But one of those kittens,
again on average, is going to be homozygous, and hence crippled and
may need to be destroyed. Breeding Fold-to-Fold can still produce anything
from all fold-ear kittens to no fold-ear kittens at all.
