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Originally Posted by Tx2Stepn What concerns me is what are the effects of recessive gene breeding. I know that in humans it is responsible for some very devistating diseases. I have a great niece with Frasier Syndrome that came from her parents recessive genes. It broke up their family and has changed their lives forever. Has any research been done on the breed to see if there are higher incedence of liver shunt or other problems that are gene related? I would be interested in reading that and learning more. For me I fell in love with the Yorkshire Terrier and have no desire to own any other breed. |
There are many "recessive" genes in all dogs...in all mammals. Recessive only means "unseen"...the gene must be carried by both parents in order to become visible. Recessive can be a good thing or bad thing....depends on what gene we are dealing with. For example......in Yorkshire Terriers the "blue silk" gene is recessive. BLACK is the dominant gene in Yorkshire terriers....."dominant" also means what you see is what you get. If two BLACK Yorkies are bred....the result will always be BLACK get...always. BUT in Yorkies....a blue dog can carry one alele of the blue and one of the BLACK.....if both parents care one blue gene then the litter will be mixed...some blue and some black. It is possible for Yorkies to only carry the recessive blue gene.....in that case....if two are bred with the reccessive (bb) gene....then blue dogs will always be the result. Problem is we don't always know what color genes the dog carries....that's why it is so difficult to breed Yorkies with the proper blue silk coat......oh the silk gene is still another problem thrown into the mix...the silk gene also has to be present....otherwise we get "clerical gray" dogs without the silky feeling coat.
Another example is the ears.....in Yorkies small upright ear is a "dominate" gene. Floppy large ears are recessive......breed two dogs with proper ears....and small upright ears will be the result...always. One correct ear and one floppy ear will result in a mixed litter. I have corrected ears in one generation by only selecting the puppies with proper upright ears...even if one parent had bad ears. With ears....what you see is what you get.
So it's the same with genetic illness.....if it's a recessive gene there is no way to know when it will surface.....until we breed two recessive carriers together....and disaster strikes. This is why breeders do line-breeding or in-breeding to condense the gene pool to test for any recessive genes the parents may be carrying. In-breeding DOES NOT create an illness......it only serves to reveal the problem so the dog/bitch can be taken out of a breeding program. It is only when we continue to breed carriers that a problem will become wide spread in a breed......remember it's recessive....so it is unseen.
AND yes!! we are pretty sure livershunt is a recessive gene....must be carried by both parents in order for a puppy to be "affected". BUT problem is we cannot idenitfy the "carriers" as it is thought to be recessive...we need the DNA marker in the worst possible way. In test breedings of two "affected" and surgerial corrected livershunt Yorkies...no affected livershunt pups resulted....thus the need for the DNA marker.
D