Some genetic conditions are caused by variants (also known as mutations) in a single gene. These conditions are usually inherited in one of several patterns, depending on the gene involved:
Inheritance pattern |
Description |
Examples |
---|---|---|
Autosomal dominant |
One altered copy of the gene in each cell is sufficient for a person to be affected by an autosomal dominant disorder. In some cases, an affected person inherits the condition from an affected parent |
|
Autosomal recessive |
In autosomal recessive inheritance |
|
X-linked dominant |
X-linked dominant |
|
X-linked recessive |
X-linked recessive |
|
X-linked |
Because the inheritance pattern of many X-linked disorders is not clearly dominant or recessive, some experts suggest that conditions be considered X-linked rather than X-linked dominant or X-linked recessive. X-linked disorders are caused by variants in genes on the X chromosome, one of the
two sex chromosomes |
glucose-6-phosphate-dehydrogenase-deficiency, X-linked thrombocytopenia |
Y-linked |
A condition is considered Y-linked |
Y chromosome infertility, some cases of Swyer syndrome |
Codominant |
In codominant inheritance |
ABO blood group, alpha-1 antitrypsin deficiency |
Mitochondrial |
Mitochondrial inheritance |
Many health conditions are caused by the combined effects of multiple genes (described as polygenic) or by interactions between genes and the environment. Such disorders usually do not follow the patterns of inheritance listed above. Examples of conditions caused by variants in multiple genes or gene/environment interactions include heart disease, type 2 diabetes, schizophrenia, and certain types of cancer. For more information, please see What are complex or multifactorial disorders?
Disorders caused by changes in the number or structure of chromosomes also do not follow the straightforward patterns of inheritance listed above. To read about how chromosomal conditions occur, please see Are chromosomal disorders inherited?
Other genetic factors sometimes influence how a disorder is inherited. For an example, please see What are genomic imprinting and uniparental disomy?
Topics in the Inheriting Genetic Conditions chapter
- What does it mean if a disorder seems to run in my family?
- Why is it important to know my family health history?
- What are the different ways a genetic condition can be inherited?
- If a genetic disorder runs in my family, what are the chances that my children will have the condition?
- What are reduced penetrance and variable expressivity?
- What do geneticists mean by anticipation?
- What are genomic imprinting and uniparental disomy?
- Are chromosomal disorders inherited?
- Why are some genetic conditions more common in particular ethnic groups?
- What is heritability?
The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.