| Subject | Contents |
| Definition | |
| Alternative Names | Inheritance - autosomal dominant; Genetics - autosomal dominant |
| Information | A single, abnormal gene on one of the autosomal chromosomes (one of the first 22 "non-sex" chromosomes) from either parent can cause the disease. One of the parents will usually have the disease (since it is dominant) in this mode of inheritance . Only one parent must have an abnormal gene in order for the child to inherit the disease. BACKGROUND: The inheritance of genetic diseases, abnormalities, or traits is described by both the type of chromosome the abnormal gene resides on (autosomal or sex chromosome), and by whether the trait (itself) is dominant or recessive. This usually translates to whether a single, defective gene (dominant inheritance) or both copies of the gene are defective (recessive inheritance). Autosomally inherited diseases are inherited through the non-sex chromosomes (i.e. chromosome pairs 1 through 22). Sex-linked diseases are inherited through one of the "sex chromosomes", the X chromosome (diseases are not inherited through the Y chromosome). Dominant inheritance occurs when an abnormal gene from ONE parent is capable of causing disease even though the matching gene from the other parent is normal. The abnormal gene dominates the outcome of the gene pair. Recessive inheritance occurs when BOTH genes of a pair must be abnormal to produce disease. If only one gene in the pair is abnormal, the disease is not manifested or is only mildly manifested. However, a person with a single defective gene is called a carrier (meaning the disease can be passed on to the children). STATISTICAL CHANCES OF INHERITING A TRAIT: For an autosomal dominant disorder: If one parent has an abnormal gene and the other normal there is a 50% chance each child will inherit the abnormal gene, and therefore the dominant trait. In other words, if it is assumed that 4 children are produced, one parent has an abnormal gene for a dominant disease, the STATISTICAL expectation is for: 2 children normal 2 children with the disease This does not mean that children WILL necessarily be affected. It does mean that EACH child has a 50:50 chance of inheriting the disorder. Children who do not inherit the abnormal gene will not develop or pass on the disease. RELATED TOPICS: Autosomal recessive Genetic counseling and prenatal diagnosis Sex-linked dominant Sex-linked recessive For detailed information, see heredity and disease ( genetics ). |
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