I can answer the part about normal parents producing retinal dysplasia. It is likely an autosomal recessive trait in most breeds. That means that if both carry the gene for retinal dysplasia, then 1/4 or 25% of their offspring will probably have retinal dysplasia. The reason we test? That's easy. If one parent has retinal dysplasia and the other clear parent carries one gene, then 50% of the offspring may have retinal dysplasia and all of them will likely carry at least one gene for retinal dysplasia. If two parents with retinal dysplasia are bred, ALL offspring will likely have retinal dysplasia. (Labradors have an autosomal dominant condition associated with retinal dysplasia but that's another story.)
Folds are hard to see between six and 10 weeks of age, due to the coloring of the tapetum at that age; folds may easily be missed in young puppies. For this reason, it is recommended that puppies be examined again at six months of age. My guess is that the puppy in question always had geographic dysplasia; it was just missed. There may not really that much difference between folds and geographic dysplasia -- a fold means that the inner retinal layer is dysplastic; geographic retinal dysplasia just means that there are larger areas of dysplasia. As far as viruses, there is some information suggesting that herpesvirus may cause retinal dysplasia in certain instances, usually in utero or in the neonatal period, but probably not in a dog of a year of age. Leanne ----- Original Message ----- So.....can anyone explain to me why we are testing at all if you > can breed a Normal to Normal and get a normal puppy who turns into a juvenile > fold that goes to geographic in both eyes by the age of two? ========================================================= "Magic Commands": to stop receiving mail for awhile, click here and send the email: mailto:[EMAIL PROTECTED]?body=SET%20CKCS-L%20NOMAIL to start it up gain click here: mailto:[EMAIL PROTECTED]?body=SET%20CKCS-L%20MAIL E-mail [EMAIL PROTECTED] for assistance. Search the Archives... http://apple.ease.lsoft.com/archives/ckcs-l.html All e-mail sent through CKCS-L is Copyright 1999 by its original author.
