Scottish Fold
Fd = Scottish Fold gene (dominant with incomplete penetrance). Cats with this gene have ears that curl forward. There are different degrees of folding, and more genes may be involved in the expression of the Fd gene. This gene is associated with bone and cartilage defects such as thickened tail and swollen feet. The homozygous form (FdFd) causes severe osteochondrodysplasia. Because of this, many breeders only breed folds to non-folds to avoid homozygous folds. However, heterozygous folds may also develop osteochondrodysplasia of lesser severity.