Make Sense of How Hemophilia is Transmitted

Edited by Lor777, Eng


It is common to find yourself still shouldering responsibility for hemophilia and looking for clues in your past behavior or medical history, especially if hemophilia does not run in your family. Hemophilia is not caused by stress, alcohol ingestion, medication taken during pregnancy, or bad behavior. It is an inherited trait, just like your hair, eye, and skin dolor. It can, also, appear spontaneously with no family history. It just happens, and no one and nothing is to blame. But, how was it transmitted? You may already know that usually only males inherit hemophilia. Why only males, and why only some males within a family?

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To understand, you must learn a bit about genetics. Inherited traits are located on genes. Within the nucleus of every one of your 3 trillion body cells, there are 50,000 to 100,000 microscopic genes, grouped together on long pieces of DNA called chromosomes. Genes are the biochemical blueprints of the body; they produce hair color and skin color, these proteins determine how your organs will develop and function, how your bones will grow, what you will look like, and how well your blood will clot. When a gene that is supposed to contain the instructions for a key biological function does not work properly, it may lead to a genetic disorder such as hemophilia.

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There are 46 chromosomes in each cell, arranged in 23 pairs. On one pair of chromosomes only lies the gene with the incorrect directions for blood clotting--the gene that causes hemophilia. It lies on the chromosome pair that determines whether you will be male or female. These chromosomes are called the "sex" chromosomes. Because the genes are found on the sex chromosomes, the appearance of hemophilia shows a definite pattern based on whether a boy or girl is created.

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Here's How the Gene with Hemophilia Found Its Way into Your Child

  1. 1
    A child is conceived when the sperm fertilizes the egg.
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  2. 2
    The sperm contains 23 chromosomes.
    They are copies of half the father's genetic makeup.
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  3. 3
    The egg contains 23 chromosomes.
    They are copies of half of the mother's genetic makeup.
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  4. 4
    When sperm fertilizes the egg, the new cell contains 46 chromosomes.
    Half of them are from the father and the other half are from the mother.
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  5. 5
    The egg contains an X chromosome.
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  6. 6
    The sperm can contain either an X or a Y chromosome.
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  7. 7
    A female is created when the sperm and egg contain X sex chromosomes.
    Every female is XX.
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  8. 8
    A male is created when the sperm contains a Y sex chromosome, and the egg contains an X sex chromosome.
    All males are XY.
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Hemophilia 01.gif

So, a Girl (XX) will develop if the first sperm to reach and fertilize the egg contains an X. A boy (XY) will develop if the sperm contains a Y. If one of the X carries the hemophilia gene then, the following will happen:

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**The girl will be a carrier (one X affected, on X not affected).
**The boy will have hemophilia (Y not affected, X affected).

One of those X chromosomes contains the hemophilia gene if the mother is a carrier of hemophilia. In a carrier mother, half of all her X chromosomes have the defective gene, because the gene for hemophilia always lies on an X chromosome. The other half are unaffected, or normal. The mother probably doesn't have hemophilia because her unaffected genes have the correct blood clotting instructions. They produce enough factor in her bloodstream, but she can pass along an affected X to her child.

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When a male baby receives an affected X chromosome from his mother, he will have hemophilia. Why? As a male, he has an X and a Y chromosome, because he has no unaffected "backup" X that could produce the correct clotting instructions. If you are a mother who is a carrier, each of your children has a 50% chance of receiving an affected X chromosome. If you have a son, there is a 50% chance that he will have hemophilia. If you have a daughter, there is a 50% chance that she will be a carrier. It's like the flip of a coin: heads, it's a boy; tails, it's a girl. If it's a boy, flip again: heads, he has hemophilia; tails, he doesn't. Sometimes life with hemophilia seems that fickle, too.

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What happens when your son with hemophilia has children of his own? Well, we're hoping for a cure by then! But beyond that, your son will contribute either an X or a Y chromosome to create an embryo. Each of his X chromosomes is affected, so all his daughters will be carriers of hemophilia. Each Y is normal, so all his sons will be unaffected. If he has sons only, hemophilia will disappear from is direct ancestry. Do girl's get hemophilia? You bet. In rare instances, a father with hemophilia and a carrier mother could produce a girl with hemophilia. There is a 50% chance each daughter and son will have hemophilia. The father with hemophilia gives an X chromosome, which carries the hemophilia gene. The mother gives an X chromosome affected by hemophilia.

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Tips Tricks & Warnings

  • When a child with hemophilia suddenly appears in the family tree, the mother may want to be tested to determine if she is a carrier.
  • The results of being tested could influence family planning.
  • The decision to be tested should always be a personal one between you and your spouse.



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Categories : Blood Disorder & Issues

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