Genetics · BEGINNER LESSON
Autosomal dominant
Autosomal dominant inheritance is a pattern where one altered copy of a gene on a non-sex chromosome can be enough to pass on a trait or disease risk. A child of an affected parent has about a 50% chance of inheriting that variant, but the exact outcome can still vary because not everyone with the variant shows the same effect.
What it is
Autosomal dominant describes inheritance of a variant on an autosome, meaning a non-sex chromosome. In this pattern, one pathogenic variant in a single gene copy can be sufficient to raise disease risk or produce a trait. Sources describe this for hereditary cancer risk, hearing loss, and several inherited syndromes. [0][1][2]
[1] Cancer Genetic Predisposition and Clinical Applications—A ... - PMC [2] Genetic Hearing Loss Overview [3] Integrating germline and tumor sequencing to improve hereditary cancer diagnosis and care
How it works
If a parent carries a pathogenic variant in one copy of the gene, each child has a 50% chance of inheriting that variant. In hereditary cancer, this can raise risk even though a second damaging event may still be needed in the tumor cell to remove the remaining working copy. That second event is often called a somatic hit, meaning a change acquired in body cells rather than inherited from a parent. [0][1][2]
[1] Cancer Genetic Predisposition and Clinical Applications—A ... - PMC [2] Genetic Hearing Loss Overview [3] Integrating germline and tumor sequencing to improve hereditary cancer diagnosis and care
Mechanisms and examples
The same inheritance pattern can appear in different diseases. In hearing loss, autosomal dominant forms are often progressive and may begin after speech develops; most affected people have an affected parent, though a new variant can also appear for the first time. In cancer predisposition, a person may inherit one altered copy and then the tumor acquires a second hit, such as mutation or loss of the remaining allele, to fully disrupt gene function in that cell. [0][1][2]
[1] Cancer Genetic Predisposition and Clinical Applications—A ... - PMC [2] Genetic Hearing Loss Overview [3] Integrating germline and tumor sequencing to improve hereditary cancer diagnosis and care
Limitations and important cautions
Autosomal dominant does not mean every carrier will definitely have disease. Penetrance is the chance that a person with the variant will show the condition, and it can be incomplete. Also, a family history can look negative if relatives were not evaluated or if the variant arose de novo, meaning for the first time in one person. [0][1]
[1] Cancer Genetic Predisposition and Clinical Applications—A ... - PMC [2] Genetic Hearing Loss Overview
SEE THE IDEA
How autosomal dominant inheritance can lead to disease risk
One altered copy is enough to be inherited in the family.
Each child has about a 50% chance of receiving that variant.
A somatic change can remove the remaining working copy in a target tissue.
The altered gene function can then contribute to cancer or another inherited condition.
Inheritance can pass the first variant through a family, while a later cell-level second hit may be needed for tumor development.
Autosomal dominant refers to family transmission; some conditions also need a later cellular change before disease appears. [0][1][2]
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Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.