What's your opinion on DM carriers - Page 3

Let's assume the experts are correct so far - DM in the GSD is inherited as a simple recessive gene. For discussion purposes, I will assume everyone reading this understands what that means....both parents must carry the gene, right? How then can a carrier or an at risk produce an at risk unless bred to another carrier or another at risk? How is that even possible?  The resulting puppies can be DNA'd as young as 4 weeks and can be placed accordingly.  The mode of inheritance is no different than how the longcoat gene is inherited in this breed, it must come from both parents. If only one parent carries the DM gene, none of the puppies will be at risks even if that parent is already suffering from DM.

Whether or not the test is valid for this breed is another topic that may be settled tomorrow or never.

It is one thing to say that carrier status does not interfere with that DOG'S health -

but if there's a chance it could eventually destroy the health of some of that dog's

OFFSPRING  ...

How would you think that could happen?

This is the method used to determine the heritability of a simple recessive trait, which is a question of probability.  Probability is the chance that a given event will occur.  With simple recessive inheritance there are three possible genes which can produce six possible combinations of breeding.

Each individual has 2 alleles which make one gene and will receive one allele (50%) from the father and one allele (50%) from the mother.  Alleles can either be dominant usually indicated by a capital letter (A) or recessive usually indicated by small letter (a).  For instance the color black is dominant (A) over the color red which is a recessive color (a), so whenever the black allele is present in the gene controlling color, then the animal will be black in color.  Since the recessive trait is unknown or hidden it often produces unhealthy or undesirable traits.  Sometimes it also provides desirable traits, like the lovely red color in Welsh Springer Spaniels.  

The 2 alleles can produce the following 3 genetic combinations.

The offspring will have one of the following combinations with one allele from the father and the other from the mother:

Homozygous AA	Free from illness and not carrier. Both parents have given the dominant allele A
Heterozygous Aa	Free from symptoms but carrier. One parent has given the dominant allele A and the other the recessive allele a. Since A is dominant over a the offspring will  not show the trait for a.
Homozygous aa	Will show the recessive trait and pass it on to its offspring. Both parents either are homozygous for a or are a carrier (heterozygous) for a.

Each parent provides one of two possible alleles to the offspring and below is the probability that an offspring will inherit the two alleles depending on the status of the parents.

AA                   x         AA parent A A AA AA AA AA AA AA	100% of the offspring will be free from the recessive trait and not carrier
AA                   x        Aa   parent A A A AA AA a Aa Aa	50% of the offspring will have AA  and are not carriers and 50% Aa and be a carrier. None of the offspring will show signs of the recessive trait.
AA                   x         aa parent A A a Aa Aa a Aa Aa	100% of the offspring will be Aa and be a carrier of the recessive trait.  None of the offspring will show the signs of the recessive trait.
Aa                    x         Aa parent A a A AA Aa a Aa aa	25% of the offspring will be AA and will not carriers. 50% will be Aa and will be carriers.  25% will be aa and will show signs of the recessive trait.
Aa                    x         aa parent A a a Aa aa a Aa aa	50% of the offspring will be Aa and be carriers. 50% of the offspring will be aa and show the recessive trait.
aa                     x         aa parent a a a aa aa a aa aa	100% of the offspring will show the recessive trait

Blitzen, you're doing a commendable job attempting to get these people to understand, but their minds are fogged by emotion. I wish there was a gene identified for old age. My dogs get old and that is sad.

Joanro, genetics don't work that way, the 50/50 then 25% then 12.5% and so on.  For instance coat color on a dog deals with A, B, E, and K loci.  Then add in the dominant and recessive, the variations of, etc.  The combinations are numerous.  Below are some pictures to get the point on just coat of a GSD

and some panels available just for coat

I understand the point you are trying to make Blitzen, and many in the vet community state breeding should not be done based on one test.  What they do say is the carriers MAY or MAY NOT develop the disease later in life.  No one knows until the dog is older and by then, he or she has been bred.  Also, once the tests are reliable and valid, why continue to breed a disease into the gene pool?  Why not try to breed it out?

LOL yeah I know, hope springs eternal. I'm done with it, nothing more left to talk about other than it's probably not wise to assume a dog or litter that is advertised as "DM free" necessarily means the dog or both parents of the litter have been tested and shown to be "normals".. OFA issues clearance numbers to carriers, so be sure to ask for that number so  you can check it on their database, they also list the result of the test. At risks will not be issued clearance numbers. The other testing lab has no database, so you need to ask to see a copy of their test results. I get a bit curious when I see a dog/litter advertised as "DM free/clear" when there are no numbers provided. Carriers are considered DM free too.

I know quite a few people who have "freaked" out. I guess it depends on who you ask. For the record, I started this discussion because I was considering a purchase on a dog who is a carrier. One person told me the dog might die at a young age because of the DM. So, the hysteria is there, depending on who you ask. Also for the record, I passed on the said dog but not because of his DM status. 

"Why not try to breed it out?"

Because it is a mutation, as I said before, even OFA will only recognize the first un tested gen only as clear because it is a mutation. The gsd breed is in bad enough shape as it is, reducing the gene pool further based on a questionable DNA test is nonproductive.
This is a rediculous premise, to wait until the dog is too old to bred to "see if it developed DM." How about collect eggs and semen, freeze store until the dogs die of old age, cut them up and let's see if they have DM....if neg, go ahead and use the eggs and sperm. Sounds about right, laboratory rats for dogs. No thanks.

Good topic I,m still sitting on the fence hoping Science will catch up and show more facts and light on the subject of DM,it does seem to be some breeders are jumping on the DM band wagon when there are still so many unknowns or how accurite or reliable DM testing is as it relates to the German Shepard breed, I really hate to see the baby thrown out with the bathwater when top working temperament seems so hard to find now as it is,if there are diseases that mimic or look close to DM doesnt this further the confusion of accurite DM testing,as I understand it the AT RISK tested dogs are the worse rated in the DNA testing for DM, have any studys been done yet to show what percent of these dogs go on to develop a DM like condition at some point in their life for example 2 percent ? 10 % or 20 % ?,,,, I see Blitzen,s point we have to be careful with people that advertize as DM free or clear when in fact they might not be.

Joanro - Hip Dysplasia is caused by abnormal development of the hip socket, some think it was originally caused by a gene mutation dealing with joint development.  How many dogs were bred with bad hips because of the idea that "[it's just a mutation,] not all dogs end up with it"? Do you not want a dog free of bad hip history?

If we know of a congenial health problem that has been shown to be hereditary, is it not responsible breeding to try to minimize the exposure in future generations? I do not believe we have such a shallow gene pool that breeding dogs with a clean genetic background will cause the breed to disappear.