Some women are carriers and there are 3 different types of hemophilia (A, B, & C) plus Von Willebrand's disease.
The reason that females are carriers is that the defective gene that results in the clotting factor deficiency is located on the X chromosome and is passed on by the mother to daughter or to son. It can't be passed on from father to son but can be passed from father to daughter. I'll explain below.
Understand something about genetics: Women carry two X chromosomes (XX) and men carry one X and one Y (XY). There must be two X s to make a female baby but only one Y is needed to make a male. Each parent contributes one chromosome to a baby. Because the mother will always contribute X chromosomes, it's the father who determines the sex of the baby and he does this by contributing either an X or a Y chromosome. Since the defective gene is on an X chromosome, when it comes to male children it will be the mother who passes on the gene. A mother may pass on the defective gene to her daughter and as long as the father isn't a hemophiliac himself, he won't contribute a second defective X gene and the daughter will just be a carrier and won't have the condition herself. If the father has hemophilia and the mother is a carrier, the daughter ends up with two defective genes and she WILL have hemophilia. This applies only to A & B, the more common forms. These occur, by far, mostly in males but they CAN and HAVE occurred in females. The gene that causes C can be passed on by either parent.
Hemophilia A: Low or no levels of clotting factor VIII. This is the most common from of hemophilia, the "classic" form. There will be prolonged bleeding even minor cuts and wounds. The largest and most common problems are internal bleeding into the joints, organs and even muscles.
Hemophilia B: Low or no levels no clotting factor IX. This form is less common than A, but leads to similar bleeding concerns.
Most people with hemophilia can lead relatively normal lives if they exercise care and caution combined with prompt and adequate treatment.
Hemophilia C: Low or no levels of clotting factor XI. This is the rarest form of the three. Unlike A and B, the risk for bleeding isn't influenced by how severe the XI factor deficiency is and this makes it more difficult to manage. Most people with the C type don't bleed spontaneously but do have unpredictable bleeding tendencies after surgery or trauma. And unlike A and B, this form affects males and females equally of Ashkenazi or Iraqi Jewish descent.
Von Willebrands disease: Technically this isn't hemophilia but because it's a bleeding disorder, I included it. It's caused by a deficiency in a clotting protein called Von Willebrand factor and this disease affects both males & females equally, unlike hemophilia.
Any hemophilia, A, B or C, is potentially lethal given the nature of the deficiency. Bleeding from head trauma poses serious risk as does bleeding into any of the vital organs.
A carrier for hemophilia is a female who carries the genetic mutation for hemophilia on one of her X chromosomes, but does not exhibit symptoms of the condition herself. Carriers can pass on the gene mutation to their children, resulting in hemophilia in male offspring. Testing can confirm carrier status.
Her father has to have hemophilia as well, and the mother is a carrier or also has hemophilia. So if we pretend that the hemophilia gene is "x", you need to have "xx" to have hemophilia. The father must have the genotype "Yx" and the mother has the have "Xx" or "xx".
There are no hard answers to this, it depends strictly on luck. The statistics are though not very good for their children. Statisically the couple have a chance of having a normal son, a daughter that is a carrier for hemophilia, a daughter with hemophilia and a son with hemophia.
XhXh - with hemophilia XhXH- carrier of hemophilia
She is a carrier of hemophilia but does not have the condition
A carrier for hemophilia is a female who carries the genetic mutation for hemophilia on one of her X chromosomes, but does not exhibit symptoms of the condition herself. Carriers can pass on the gene mutation to their children, resulting in hemophilia in male offspring. Testing can confirm carrier status.
Her father has to have hemophilia as well, and the mother is a carrier or also has hemophilia. So if we pretend that the hemophilia gene is "x", you need to have "xx" to have hemophilia. The father must have the genotype "Yx" and the mother has the have "Xx" or "xx".
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Anyone can inherit hemophilia. In most cases, it is a man whose mother is a carrier of the disease. It is extremely rare for a woman to have hemophilia but it is not uncommon for one to be a carrier. It is even possible for someone whose family has no record of hemophilia to get it through gene mutations.
There are no hard answers to this, it depends strictly on luck. The statistics are though not very good for their children. Statisically the couple have a chance of having a normal son, a daughter that is a carrier for hemophilia, a daughter with hemophilia and a son with hemophia.
She is a carrier of hemophilia but does not have the condition
If the father has hemophilia and the mother is a carrier, sons will have a 50% chance of having hemophilia. Daughters will have a 50% chance of having hemophilia and a 50% chance of being a carrier. It is very rare for both parents to have these defective genes.If the father does not have hemophilia and the mother is a carrier, sons will have a 50% chance of having hemophilia. Daughters will have a 50% chance of being carriers.If the father has hemophilia and the mother has normal blood, all sons will be normal and all daughters will be carriers.
XhXh - with hemophilia XhXH- carrier of hemophilia
Normally a woman is only a carrier of hemophilia, but if her mother is a carrier and her father has hemophilia the female does have a chance to get it. It is very rare for this to happen but It has been recorded.
In a pedigree chart, Sam would be represented by a filled square (male) or circle (female) to indicate that he has hemophilia. Since Sam's brother, mother, and father do not have hemophilia, they would be represented by unfilled squares (male) or circles (female). However, Sam's mother would be a carrier of the hemophilia gene, so she would be represented by a half-filled circle. The pedigree would show Sam with hemophilia, his mother as a carrier, and his brother, father, and other family members without the disorder.
Hemophilia is a X linked recessive disorder. Usually the mother is an unaffected carrier and her son unfortunately receives the X chromosome in which hemophilia is linked to.