Genetic testing is fascinating for chickens. Ladyhawk's vet was doing a study on dwarfism in chickens and tested her two (now deceased, sadly) progeny out of my Delawares, who were occasionally and unexpectedly throwing dwarfs. It was a bizarre coincidence and allowed us a window into this genetic anomoly. These were not just small birds, but a different type of dwarfism that showed parrot beaks, crooked toes, short and a mongoloidish look to the eyes. They didn't live to adulthood.
The testing found, in one of the two hens, who was a huge bird, that she was carrying a TWO copies of the dwarf gene! He said it was definite and something most didn't think was possible, that her progeny would very definitely show dwarfism. Needless to say, she was never reproduced. Her much smaller half sister had NO dwarf gene. Interesting, huh?