canine genetics

[MCALVO]

This is a hypothetical question a friend of mine presented me with the other day. I thought I'd present it to the forums for some feedback. If you have a dog that is 3/8 mastiff and 5/8 boxer and breed it with at dog that is 1/2 mastiff and 1/2 boxer is there a possibility of the two breeds spearating back out? I.E. a genetically homozygous mastiff and a genetically homozygous boxer. This of cousrse would probably produce a myriad of puppies in between too.
A disclaimer to myself and this question. No, I do not have dogs that are of this genetic makeup and nor would I plan on breeding them if I did.
Theoretically I believe it is genetically possible. I wanted to see what the experts had to say. I thought it was an interesting question posed by a 10 yr old

 

[JulieM]

I suppose it would be possible, but it would certainly be vastly remote! With the number of genes that determine breed, the chances of only Boxer genes going to some puppies and only Mastiff genes going to others are, I'd estimate, in the millions....

It's more possible that you'll get some puppies that *look* very much like Boxers, and others that look very much like Mastiffs, but genotypically they would still be mixed.

It's like that movie, "Turner & Hooch" - where Hooch mates with the Collie and they get 4 Collie pups and one Hooch pup - that just wouldn't happen!