Why does hemophilia occur more often in males

The daughter will not have hemophilia since the normal blood clotting gene from her mother is dominant. It won't allow the instructions from the hemophilia gene to be sent. The daughter is called a carrier for hemophilia. She has the gene on one of her X chromosomes and could pass it on to her children. Does this mean that the mother alone is the one responsible for having a child with hemophilia?

Not really. The mother is the one who passes the hemophilia gene. However, it is the father's sperm that determines if the child will be a boy or a girl. It is not the "fault" of one parent since both parents contribute to the outcome. All of us have dozens of abnormal genes. We are unaware of most of them. It is purely by chance that a hemophilia gene is passed on to produce a child with hemophilia.

These four points are explained below. In other words, if carriers each had two sons 1, total , we would expect there to be about boys with hemophilia. But in that group there would be women who had two sons with hemophilia, women who had one with and one without, and women with no sons with hemophilia. The gene a child will inherit is based purely on chance and can never be truly predicted. A child's chances of getting a hemophilia gene do not have anything to do with whether or not brothers or sisters have the gene.

Each time a woman is pregnant, her chances of having a child with the hemophilia gene are the same Figure It is like rolling dice. The results of one roll do not affect the next roll. A family may have children with the hemophilia gene and children without it. It is also possible for all the children in the family to inherit the normal gene or all to inherit the hemophilia gene.

Figure For a mother who carries the hemophilia gene, the chances of giving birth to a child with hemophilia are the same for each pregnancy. Even though she already has a child with hemophilia, she can still give birth to another.

The father's sex chromosomes are labeled XY, with the X chromosome carrying the hemophilia gene. If the baby gets the Y chromosome from the father it will be a boy. Since the Y chromosome does not carry the hemophilia gene, a son born to a man with hemophilia and a woman who is not a carrier will not have hemophilia. If the baby gets the X chromosome from the father it will be a girl. The X chromosome from the father with hemophilia will have the hemophilia gene.

But the girl also gets an X chromosome from her mother. The normal blood clotting gene on the X chromosome from the mother is dominant, so the baby girl will not have hemophilia. She will, however, be a hemophilia carrier since she has the hemophilia gene on one of her X chromosomes. Mutations in the F8 or F9 gene lead to the production of an abnormal version of coagulation factor VIII or coagulation factor IX, or reduce the amount of one of these proteins.

The altered or missing protein cannot participate effectively in the blood clotting process. As a result, blood clots cannot form properly in response to injury. These problems with blood clotting lead to continuous bleeding that can be difficult to control. The mutations that cause severe hemophilia almost completely eliminate the activity of coagulation factor VIII or coagulation factor IX. The mutations responsible for mild and moderate hemophilia reduce but do not eliminate the activity of one of these proteins.

Another form of the disorder, known as acquired hemophilia, is not caused by inherited gene mutations. This rare condition is characterized by abnormal bleeding into the skin, muscles, or other soft tissues, usually beginning in adulthood.

Acquired hemophilia results when the body makes specialized proteins called autoantibodies that attack and disable coagulation factor VIII. The production of autoantibodies is sometimes associated with pregnancy, immune system disorders, cancer, or allergic reactions to certain drugs.

In about half of cases, the cause of acquired hemophilia is unknown. Hemophilia A and hemophilia B are inherited in an X-linked recessive pattern. The genes associated with these conditions are located on the X chromosome, which is one of the two sex chromosomes.

In males who have only one X chromosome , one altered copy of the gene in each cell is sufficient to cause the condition. In females who have two X chromosomes , a mutation would have to occur in both copies of the gene to cause the disorder.

Because it is unlikely that females will have two altered copies of this gene, it is very rare for females to have hemophilia. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons. In X-linked recessive inheritance, a female with one altered copy of the gene in each cell is called a carrier. Carrier females have about half the usual amount of coagulation factor VIII or coagulation factor IX, which is generally enough for normal blood clotting.

However, about 10 percent of carrier females have less than half the normal amount of one of these coagulation factors; these individuals are at risk for abnormal bleeding, particularly after an injury, surgery, or tooth extraction. But there is a 1 in 2 chance that a son will have inherited the gene and will have the trait or disorder. Examples of X-linked recessive conditions include red-green color blindness and hemophilia A:. Red-green color blindness. Red-green color blindness means that a person cannot see shades of red and green usually blue-green.

But they can otherwise see normally. This condition has no serious complications. But people affected may not be able to work in certain jobs such as transportation or the Armed Forces, where seeing color is required.

Males are affected more often than females because the gene is located on the X chromosome. Hemophilia is a disorder in which the blood cannot clot correctly because of a lack of a clotting factor called factor VIII. This results in heavy bleeding that will not stop, even from a small cut. People with hemophilia bruise easily and can have internal bleeding into their joints and muscles.