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How are autosomal dominant disorders passed through families?
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human genetic disease
Photomicrograph of the BRCA2 tumor suppressor gene on chromosome 13 of the human genome. Inactivation of this growth-regulating gene is associated with a higher risk of developing breast cancer.
Autosomal dominant disorders are passed through families when an individual inherits a single copy of a mutant gene from one affected parent. Because the trait is dominant, it manifests in the heterozygote, meaning the presence of one mutant gene is sufficient to cause the disorder.12
Key aspects of this inheritance include:
- Transmission: The disorder can occur in either sex and be transmitted by either parent. An affected heterozygote has a 50 percent chance of passing the mutant gene to each of his or her children.13
- Family History: These disorders typically show a vertical pedigree, appearing in multiple generations. However, they can also arise from new, spontaneous mutations in individuals with no family history of the condition.123
- Variable Expression: Clinical severity can vary significantly among family members due to modifying genes or environmental factors. Some individuals who carry the mutation may be nonpenetrant, meaning they show no apparent symptoms but can still pass the gene to their offspring.12
- Homozygosity: If a child inherits the mutant gene from both parents, they are homozygous. This condition may be equally affected, more severely affected, or sometimes lethal.1