Genes Fd, fd

Gene Fd (= Folded ears) Gene Fd causes the ears to fold forward and sideward. Fd is dominant over fd. Therefore gene Fd must be present only once (Fdfd) that its effect on the ears is visible. Gene Fd is incompletely dominant. Folding of ears may be expressed individually differently. Some cats have loosely forward folded ears, some cats have tight folded ears close to the head like a cap.	Gene fd (= no Folded ears) Gene fd is recessive, that means, gene fd must be present twice (fdfd) that the ears are straight.	Possible gene combinations FdFd homozygote for Folded ears A cat must have at least Fd- to have folded ears. Fdfd heterozygote for Folded ears fdfd homozygote, no Folded ears The cat has no folded ears.
The best known breed is the Scottish Fold.

Breeding program of Scottish Fold

The homozygote Scottish Fold may be affected by the so called "crippling effect" (Osteochondrodysplasia), which results in a shorter, thickened and less flexible tail and in swollen legs and problems in the joints.
There are many discussion about the Scottish Fold, unfortunately very emotional and quite subjective and lacking objectivity, especially when discussed by animal protection organizations. All reports and literature refer to studies, which are already more than 30 years old. A systematic study about this breeds does not exist, unfortunately.

It is rather interesting that already in Genetics for Cat breeders and Veterinarians, 4th edition, 1999 it is something written, which critics like to ignore and overlook simply:
Page 192: "Folded ears [cosmetic]
The homozygote FdFd has the folded ear, but it also may be afflicted with crippling epiphyseal dysplasia which results in a short, thickened tail, swollen feet and a marked decrease in activity. This condition was once prevalent in Scottish Fold cats but now appears to have been significantly reduced in incidence by selective breeding."
It is interesting that the anomaly (chapter Specific Anomalies, page 186ff) is classified as cosmetic and what one can read here in the last sentence.

As all Scottish Fold of today are mostly heterozygote, because American Shorthair or British Shorthair are used for breeding and mating Scottish Fold x Scottish Fold is not done, these problems do appear very seldom.
Unfortunately the Scottish Fold Straight, Scottish Fold with straight ears, which is the result of mating with British Shorthair, is not recognized in all organizations like the Scottish Fold that it may receive the same titles.

I had developed breeding rules for the Scottish Fold with the Estonian FIFe-member, which have been removed by FIFe from its web site. That shows evidently, how much some organizations care about breeding special breeds.

• No mating Scottish Fold x Scottish Fold

• Only mating Scottish Fold x American Shorthair or Scottish Fold x British Shorthair or Longhair

• All cats used for breeding must have a health certificate with an X-ray.

• Scottish Fold with straight ears are registered as Scottish Fold Straight, they are neither registered as American Shorthair nor as British Shorthair/Longhair.
  They are also not used for breeding American Shorthairs nor for breeding British Shorthair/Longhair.

• Recommendation: No mating Scottish Fold Straight x Scottish Fold.

Therefore one has to wait, which results the research about the Scottish Fold in the  Feline Genome Project of Dr. Lyons will show.