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Overview of Mendelian inheritance

Benjamin A Raby, MD, MPH
Section Editor
Anne Slavotinek, MBBS, PhD
Deputy Editor
Jennifer S Tirnauer, MD


Most clinical disorders with a genetic basis result from complex interactions between multiple genes (multigenic) and environmental factors, termed multifactorial inheritance. Monogenic disorders (genetic disorders caused by mutations in only one gene) are relatively rare and are often first recognized clinically by their predictable patterns of inheritance in families.

Predictable, single gene patterns of inheritance were first observed in plants by an Augustinian monk and botanist, Gregor Mendel (Mendelian inheritance) [1]. Based on observations from a large series of cross-breeding experiments of plants with varying flowering characteristics, Mendel proposed his Laws of Inheritance. These laws were soon translated to the clinical setting by Sir Archibald Garrod and launched the study of medical genetics [2].

The explosion in the field of medical genetics, following sequencing of the human genome and the more recent development of next-generation sequencing technologies, has led to identification of numerous specific genes associated with human genetic disorders. Whereas in 1990 the genetic basis was known for fewer than 2 percent of Mendelian diseases, in 2011 the molecular basis is understood for nearly 40 percent of these conditions, giving rise to more accurate diagnostic testing and the promise of novel treatments to be developed [3]. With the advent of whole genome and whole exome resequencing methods, it is likely that the majority of variants underlying the remaining monogenic diseases will be mapped within the next few years.

This topic will review Mendel's Laws of Inheritance and link these laws to our modern understanding of molecular genetics. Patterns of monogenic inheritance and means of recognizing them in the clinical setting will be described. A brief overview of the major causes of non-Mendelian inheritance is presented. A discussion of genetic variation and a glossary of terms related to genetics are presented separately. (See "Overview of genetic variation" and "Genetics: Glossary of terms".)


The following terminology is used in describing Mendelian traits and Mendelian inheritance patterns:


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Literature review current through: May 2017. | This topic last updated: Nov 03, 2016.
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