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The GeneEd website is scheduled to be retired on March 31, 2019. Selected GeneEd content will be transferred to Genetics Home Reference, another online resource from the National Library of Medicine.

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Multifactorial Inheritance/Complex Disease

Multifactorial Inheritance/Complex Disease

A complex disease is caused by the interaction of multiple genes and environmental factors. Complex diseases are also called multifactorial. Examples of complex diseases include cancer and heart disease.

Materials for Multifactorial Inheritance/Complex Disease



Description: Learn in detail how genes code for crest, the feathers on the head of some pigeons. Learn about alleles, inheritance, and modifier genes.


Description: A well illustrated article that makes explaining epistasis a breeze. In a nut shell, epistasis describes how different versions of a gene affect complex, multi-step processes.

Foot Feathering

Description: Learn in detail how genes code for foot feathering on pigeons. Learn about genes, inheritance, and complex traits.

Genetics: Complex Inheritance Patterns

Description: An article and short activity using blood type to teach concepts of complex inheritance

Multifactorial Inheritance

Description: Information on multifactorial inheritance, including a chart showing the percentage of genes shared in common with first, second, and third degree relatives; also examples of conditions with multifactorial inheritance

Multifactorial Inheritance and Genetic Disease

Description: An article on multifactorial inheritance

Multifactorial Traits

Description: A listing of the characteristics of multifactorial traits

Recessive Red

Description: Some pigeons, well, do not even look like pigeons. Learn more about what makes this bird an eye catcher.

What Are Complex or Multifactorial Disorders?

Description: A description of multifactorial inheritance

What Is a Complex Disease?

Description: Many common diseases are influenced by a combination of multiple genes and environmental factors. These diseases are referred to as complex diseases.


DNA Roulette

Description: This odds game makes learning about the probabilistic nature of genomics a blast. Unlike traditional roulette where the betting table and odds are always the same, DNA Roulettes odds are different for each disease or trait. Even within a disease, the odds are different depending on which of several possible genotypes is randomly selected by the game engine for that round.

Dog Breeding

Description: Practice breeding dogs to get a puppy with certain single and multigenic traits

Interactive Tutorials

Mendelian Genetics Cannot Fully Explain Human Health and Behavior

Description: An interactive Web site exploring basic concepts of multifactorial inheritance through historical discovery

Teacher Resources

Complex Trait Genetics (PDF 2,053.35 KB, Lesson Plans/Lesson Activities)

Description: The lesson begins with students contrasting histograms of a discrete trait (sex) and a continuous trait (height). Students then explore polygenic inheritance of height with a three-gene system, in the process modeling segregation of alleles and independent assortment during meiosis, as well as sexual reproduction. Finally, students discuss limitations of their model and add environmental influences.

Genes, Environments, and Behavior (Lesson Plans/Lesson Activities)

Description: This lesson focuses on how behavior is defined by scientists and on the genetic and environmental forces that interact to shape behavior.

Genes, Environments, and Behavior 2 (Lesson Plans/Lesson Activities)

Description: This lesson helps students understand how scientists study the genetic and environmental factors that interact to produce variation in behavior across a population.

Introduction to Complex Inheritance (Lesson Plans/Lesson Activities)

Description: At the beginning of this lesson, students' prior understanding of non-Mendelian (complex) inheritance, the nature of genetic information, and how genetic information can be used is assessed using a Genetic Pretest and a creative writing assignment. Then, students learn about some of the many complexities of inheritance of non-Mendelian traits.

It is Genetic--Or Is It? (Lesson Plans/Lesson Activities)

Description: This lesson for grades 9-12 explores the age-old discussion of nature vs. nurture: how much of our individuality is based on inheritance, and how much is shaped by our environment? Students explore different traits as genetic or environmental and then discuss issues of accountability for genetically-influenced personality traits.

Multifactorial Traits (PDF 2.53 MB, Lesson Plans/Lesson Activities)

Description: Detailed book chapter on multifactorial traits with practice problems

Nature and Nurture (Lesson Plans/Lesson Activities)

Description: In this lesson, students develop an understanding of the role both nature and nurture play in determining human traits.

Pets - Oh Behave (Lesson Plans/Lesson Activities)

Description: This lesson helps students develop an understanding of how innate and learned behaviors and the environment determine behavior.

The Chernobyl Disaster (Lesson Plans/Lesson Activities)

Description: Students explore how a nuclear accident can affect biological systems.

The Mystery of Calico Cats (Lesson Plans/Lesson Activities)

Description: In this lesson, students explore the genetics and epigenetics behind calico cats. Using sex-linked Punnett squares, students must determine what the genotype for coat color is for calico cats. The class then discusses why dosage compensation for the X chromosome is necessary in females and how that relates to the patchy appearance and female sex of calico cats.

What Makes Honey Bees Work Together? (Lesson Plans/Lesson Activities)

Description: A series of lesson plans exploring how genes and environment affect behavior, as well as introduces students to research tools used to investigate gene expression. You may need to register to view the lesson plans, but the plans and registration is free.