Hemophilia is a genetic disease. This means
that the disease is passed down through the generations by means of our
genetic codes, or genes. Humans are made up of 46 chromosomes which have
the battle plans for various functions, actions, and makeup of the body.
These are 23 chromosome pairs. Chromosomes also determine whether or not
we will be male or female. These two chromosomes labeled "x" and "y". A
male will have one "x" and one "y" and females will have two "x"'s. Usually
males are the only ones who get hemophilia. Hemophilia is found on the
"x" chromosome at the very bottom and when it occurs people suffer from
the inability to form firm clots. Which, means in short, that they bleed,
and keep bleeding.
The reason that more males get the disease is quite simple. Since the disease occurs on the "x" chromosome, if a male's "x" chromosome has the disease, he doesn't have another "x" to block it out. But a female on the other hand has two "x" chromosomes so if one has the disease, she has another "x" to block it out. So, if a female has only one "x" diseased she is called a carrier, so she has the disease in her, but it doesn't show up. A male is always a hemophiliac.
In reality there are two different kinds of hemophilia that act alike. Hemophilia A (factor VIII deficiency) and Hemophilia B (factor IX deficiency) This protein deficiency causes the blood to not be able to form a firm clot, and thus a hemophiliac who gets bruised or cut, keeps on bleeding. Not more, but longer. There are also other blood clotting disorders such as von Willebrand disease which can affects both sexes.
Another tool that scientists use is called a Punnett Square. This shows the possible outcomes of a child birth between a male and female. If you look to the left, you see an example of a Punnett Square. The male is on the top of the square, and has hemophilia because his one "x" chromosome has the disease. (represented by the small "h") The female is completely clean from the disease. All of the people represented inside the box are the possible offspring. In this case, if the couple have a daughter, it will be a carrier no matter what. (represented by one of the "x"'s having the disease) If the couple has a son, he will be completely ok no matter what.
picture is another Punnett Square. In this picture the woman is just
a carrier and actually doesn't show any signs of the disease. As you can
see, the result of this birth could be much worse than before. If this
couple had a son, they would have a 50% that their son would have hemophilia.
This is a good example how the disease can hide in the generations of people,
and show up every once in a while in its full blown form.