Quote:
Flower, it's a numbers game.
Each chick gets one gene from each parent. The parents each have have two copies of the same gene (one from each of their parents).
Let's assign colors and assume green means Na (yes! to naked neck) and red means na+ (no to naked neck).
So the chick-to-be goes to the father who has TWO green genes because he is a pure naked neck. It picks ONLY ONE of his genes. But because they are BOTH green, it does not make a difference. Now the chick-to-be goes to the mother (who is a pure leghorn and therefore has TWO red genes) and picks ONLY ONE of her genes. But because they are BOTH red, it does not make a difference. ALL chicks will end up with ONE green and ONE red. That means they all look like naked necks but their genes are only HALF naked neck, hence Na na+.
So now one of these chicks becomes a father. Remember, he has ONE green and ONE red gene. The next generation chick-to-be goes to the father and picks a gene. You can safely assume that 50% of the time it will be ONE red gene and 50% of the time it will be ONE green gene. Mix that now with the guaranteed red gene from the leghorn mother. In this generation the 50% of chicks that picked the green gene from the dad will look like naked necks (although they are genetically only HALF naked necks and half feathered necks) and the other 50%? Those poor fellows picked the red gene from the dad and end up with ONLY red genes. They will have a feathered neck for sure and so will all their offspring.
Dominant means that if a green and a red gene are present at the same time, the green gene wins! Hence chick will look like naked neck. But if the chick does not pick the green gene dominance does not work because there is nothing there!