I have a question on the genetics of size. I'll use dogs, since it's a good example since they vary greatly in size. Okay, try not to laugh when reading this question: If a 2-pound male chihuahua fathered puppies with a 200-pound female mastiff, about how big will the offspring be when full grown? Will they be closer to the midpoint (~101 lbs.), or would they be closer to the geometric average (~20 lbs.)? Are there dominant/recessive genes that control size?

A fair amount of googling only revealed a bunch of other people wondering the same thing. You might be able to make an educated guess based on less extreme cross-breeds like the "saint berdoodle" (crosses between a saint bernard and a poodle), which seems to be closer in size to the saint bernard, which of course is neither the arithmetic nor geometric mean, so apparently its not that simple (I don't know what the mechanism is). Looks like we'll just have to perform the experiment ourselves.

IIRC, both miniaturization and gigantism in dogs are the product of hormonal abnormalities (deficiencies and excesses, respectively). A breeding of either of these unusually sized dogs with something outside of their size range (and therefore possessing the genes for normal hormones) should result in something a lot closer to a normal dog size.