Originally Posted by farmpony84
And if a horse tests positive for the homozygous gene that means that it will produce a lethal white?
If you breed a white horse to a non-white horse you have a 50% chance of a healthy white foal and a 50% chance of a healthy, non-white foal.
If you breed a white horse to another white horse, you run a 25% chance of a healthy, non-white foal, a 50% chance of a healthy, white foal, and a 25% chance of a lethal foal. Though in the case of dominant white, as opposed OLWS, I think the lethal form more frequently ends in abortion and late-term pregnancy termination rather than a live birth which soon dies.