This is a visual for the explanation of what has been said about sex-linked genes.
The sex-linked trait does not necessarily have to be recessive. There are some that are dominant, such as the human form of rickets. To understand sex-linked, one of the easier traits to notice is color blindness.
This is actually present in my family. My mother is one of the "rare" females that end up with both affected X chromosomes. Because she has two "bad" X's, no matter how many brothers I have, they will ALL be color blind. Because of my father though, I am not. He is not color blind and therefore has a normal X. I had to receive that normal x because I am female. This means that the chromosome I received from my father covers up the "bad" X I received from my mother.
I could go on and on about how there is a 50% chance of any boys I have being color blind, but that could get really confusing really quickly.
Overall, I hope that the image helps. I saw what loki had written and figured that this might be a little easier to understand.
"The true work of art is but a shadow of the divine perfection." ~Buonarroti Michelangelo
I'm just an observer, loving the game...