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Autosomal dominant inheritance
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Everybody has two copies of each of their genes, which are inherited from their
parents. One copy is inherited from the father and the other from the mother (there
are about 60,000 different genes, and
two copies of each).
In autosomal dominant inheritance, a single copy of an abnormal gene is enough for
clinical signs of the disease to appear. This is because both the healthy gene and
the abnormal gene are equally active. In this inheritance pattern, both males and
females are affected equally and with the same degree of severity.
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An affected person has a 50% risk of transmitting the abnormal gene to his children.
The risk that healthy parents who have an affected child will have another affected
child is low, as in most such cases a new mutation has arisen in the ovum or sperm
cell that formed the child. An example of a disease transmitted by autosomal dominant
inheritance is
achondroplasia (one of the more common forms of short stature).
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