Inheritance patterns of monogenic disorders (Mendelian and non-Mendelian)
- Benjamin A Raby, MD, MPH
Benjamin A Raby, MD, MPH
- Section Editor — Genetics
- Associate Professor of Medicine
- Harvard Medical School
Monogenic disorders (monogenic traits) are disorders caused by variation in a single gene and are typically recognized by their striking familial inheritance patterns. Examples include sickle cell anemia, cystic fibrosis, Huntington disease, and Duchenne muscular dystrophy.
By contrast, complex disorders (complex traits) are those in which multiple genes play a role, often together with environmental factors. These include many complex disorders such as cardiovascular disease, asthma, diabetes, and cancer susceptibility.
This topic review discusses the inheritance patterns of monogenic traits, including classic Mendelian inheritance patterns as well as non-Mendelian patterns of inheritance such as mitochondrial inheritance and sex-linked expression, variable expressivity, variable penetrance, and other effects.
Complex (multigenic) disorders and an overview of the causes of genetic variation are discussed in detail separately. (See "Principles of complex trait genetics" and "Basic principles of genetic disease" and "Overview of genetic variation".)
A glossary of genetic terms is also presented separately. (See "Genetics: Glossary of terms".)
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- BASIS FOR MONOGENIC TRAITS
- MENDELIAN INHERITANCE PATTERNS
- Overview and definitions
- Autosomal dominant
- Autosomal recessive
- CAUSES OF NON-MENDELIAN INHERITANCE
- Penetrance and expressivity
- - Incomplete or variable penetrance
- - Variable expressivity
- - Causes of incomplete penetrance and variable expressivity
- Parent-of-origin effects (imprinting)
- Mitochondrial inheritance
- Sex-limited expression
- Multigenic disorders
- - Digenic
- - Triallelic
- - Complex traits
- CLINICAL RELEVANCE