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I just really don't know much about it. I've heard it can cause defects if continually done. And also a shorter lifespan. I am just not sure. Are there any pros? Well, I really want to know, and if your dog was inbred but it was far back in ther history, could t still cause problems? What's your personal opinion on this? Just wondering . Hehehe, thanks everyone!
Zeebles

Inbreeding doesn't cause defects, it exposes them. Inbreeding reduces heterozygosity in a population, so if a condition (good or bad) is expressed only if the animal is homozygous for that trait, then inbreeding over time will increase the likelihood of that trait appearing at a higher frequency in the population. When done with a goal in mind and a solid understanding of patterns of inheritance and the pedigree's of the animals you are working with, inbreeding can be beneficial.

To understand inbreeding you have to know a little bit about genetics.

1) every mammal (people, dogs, cats, etc..) has 2 copies of every chromosome one copy if from Mom and one copy is from Dad.
2) each chromosome has a bunch of genes on it so each individual has 2 copies of each gene. These can be the same (Homozygous) or different (heterozygous).
3) genes are just information they produce a protein which actually does work in the body
4) different versions of a gene produce proteins that are better or worse at their job.
5) Chromosomes mutate all the time I estimated every dog should have around 10 new mutations not counting any they inherited from their parents. Mutations are caused by lots of things like radiation, oxygen, chemicals and just inherent flaws in biological systems when the chromosomes are replicated (ei. when a cell divides).
Mutations create new versions of genes which can be better or worse or the same at their job. Most are either a little bad or the same, some are very bad, and only a tiny number are good.
6) if an individual is homozygous for a gene that doesn't produce a working protein then you usually get a genetic health problem (depending on the gene it could be a bit bad or fatal). However, if an individual is heterozygous for a non-working gene often if the other copy they have works well they will be fine. You can also have individuals which are homozygous for good working genes which are also fine. The problem is it is usually impossible to tell a homozygous good from a heterozygous individual.

Putting this all together means that every dog has several slightly bad versions of genes which have no effect on the dog because they have a good copy but which can be passed on to their offspring. And there is a chance that any dog could have a very bad version of a gene and you wouldn't know it.

When you inbreed there is a higher chance of getting 2 identical copies from the same parent just by chance. If the copies are bad then it will have a negative effect on the health of the dog.

eg. Bitch B and stud S are bred. stud S has a version of a gene involved in preventing cancer which doesn't work.
A daughter from this litter is bred back to stud S.
Now there is a 50:50 chance the daughter got the bad cancer gene.
if the daughter has the gene then there is a 50% chance she will pass it to the pups, Stud S does have the gene so there is a 50% chance he will pass it to the pups as well.
So all together there is a 12.5% (.5*.5*.5) chance a pup from a daughter of S bred back to him will have 2 copies of the bad cancer gene. And thus have a much higher chance of getting cancer. By itself this doesn't seem too bad but if this is continued over many generations the probability will get higher and higher.

On the other hand if your trying to create a new breed of dog that only comes in brown and stud S has a version of a gene that results in brown. Then breeding a daughter back to him will give a 12.5% of homozygous brown pups if these homozygous brown pups are bred together then all the pups will be brown. As you can see inbreeding can be used to very quickly breed in an interesting mutation (eg. a mutation for colour).

Remember though that in each example we just followed one gene of interest but there are thousands of genes in every dog and inbreeding doesn't discriminate between bad and good.
so if Stud S have both the gene for brown and the bad cancer gene then there would be a 12.5% chance that a brown pup will also have a high chance of cancer.

grif,

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