Breeding within the family

[kc261]

You have to take into consideration that either the father or mother has a different father/mother than the offspring they produce, so the only similar genetics are of whichever parent you breed the offspring to, when two siblings however are bred together they have no genetic diversity since they have both the same mother and father. Although it most likely wouldn't cause concern for problems breeding sibling to sibling, you still have the higher chance of a problem occuring.

I might be missing something, but I just did the math again, and I still come up with equal possibilities either way. I used an example where you have a snake carrying a recessive gene for a deformity. Since the snake is only het, you have no idea it is carrying this gene. You mate it with another snake that does not carry this bad gene. 50% of the offspring will be het for the deformity. I went through all the possible pairings, offspring to parent and sibling to sibling, and when I added it all up, the chance of getting deformed offspring in the next generation was the same for offspring to parent as it was for sibling to sibling. If anyone wants, I'll post the way I worked it out, but it will be long.

One place where sibling to sibling would be worse is if both parents carry bad genes, but different bad genes. Say the male carries a gene for blindness and the female carries a gene for deafness (I know...not the best example with snakes...). Then with sibling to sibling you have a chance of getting a snake that is both blind and deaf. However, I'm assuming you don't know if any snakes carry any bad genes, otherwise you wouldn't breed them at all. In that case, it is just as likely that both the blind and deaf gene are carried by the same snake, in which case, I believe (although I didn't actually work out the double het) pairing offspring to parent would make it more likely you'd get the double deformity than sibling to sibling. Or maybe it would still stay equal because 50% of the time you'd be pairing to the parent that carries neither gene.

Perhaps your error is in the statement "when two siblings however are bred together they have no genetic diversity since they have both the same mother and father". Actually, there should still be quite a bit of genetic diversity. Siblings do not have identical genes to each other, except identical twins. It is even possible that they do not have any genes in common at all. Remember that although each child gets half of their genes from each parent, there is nothing to say that the next child gets the same half. That is why in my previous post I said that siblings share 50% of their genes, on average.

Does anyone else know anything more definitive on this subject?