Dog with only 1 testicle?

Simplified:

This is the result of a recessive gene...which means that the dog's sire was carrying it, although it didn't affect him. In order for recessive genes to express, the puppy must receive copies of it from both parents (meaning that the dog's dam was carrying it, too). This doesn't always happen...the other puppies in the litter received at least one copy of the dominant version of the gene (in this case, having two descended testicles), which means that some or all of them are also carriers for the problem, although they aren't affected by it. They can, however, pass it on to their own offspring if bred.

ADD: More detailed information on inheritance:

http://www.upei.ca/~cidd/Diseases/urogenital%20dis...

This is caused by a recessive gene, and both sides need to be carriers, or affected. With the offspring, some will be affected, some will be carriers, and the small remaining percentage will be unaffected. It's Mendel's theory (genetics). It's just Sods Law that this puppy happens to be the affected. However, it is good that he's being neutered because retained testicles will most likely become cancerous so it needs to be located, and removed. Obviously the breeder will, hopefully, know not to repeat this pairing, or closely related animals either as the fault is in there somewhere.

Don't worry, he'll be fine, once he's neutered.

ps Dogs with only one testicle are called Monorchids. Cryptorchids have neither descended.

This is a very common genetic problem. There is no rhyme or reason as to why one male puppy has the condition or not. However when this does occur some breeders will not repeat having a litter with that particular breeding pair in order to purge the genetic defect.

Most of these pups do have two testicles only one of them has not descended. The risk is that if the non-descended testicle is left in the abdominal cavity, the pup has a markedly increased risk of developing testicular cancer.

Animal_atwork is correct! While they can still fathered puppies, it's a generic defect, and will be passed on to the male pups. It's highly recommendable that a dog affected with cryptorchidism to be neutered as soon as possible, to avoid the risk of cancer.

Somewhere along the line it was passed on. Good thing he's getting neutered. The testicle that did not come down can turn cancerous.

Could be in the mother's lines as well. Pups get 50% of their genes from the mom.

Just something that happens from time to time, chances are his only family had both, just happened to happen with him, no worries nothings wrong.

It has two;one is just up in the abdomen.

Cryptorchids happen......everywhere.....all breeds & mutts.

some are just simply less fortunate. that ball is somewhere though, im sure one of his brothers has 3...