What is a Polygenic Inheritance?

Mary McMahon
Mary McMahon

The term “polygenic inheritance” is used to refer to the inheritance of quantitative traits, traits which are influenced by multiple genes, not just one. In addition to involving multiple genes, polygenic inheritance also looks at the role of environment in someone's development.

Polygenic inheritance refers to any trait, such as human skin color, that can be expressed in varying gradients because it is influenced by multiple genes.
Polygenic inheritance refers to any trait, such as human skin color, that can be expressed in varying gradients because it is influenced by multiple genes.

Because many traits are spread out across a continuum, rather than being divided into black and white differences, polygenic inheritance helps to explain the way in which these traits are inherited and focused. A related concept is pleiotropy, an instance where one gene influences multiple traits.

Early Mendelian genetics focused on simple traits that could be explained by a single gene.
Early Mendelian genetics focused on simple traits that could be explained by a single gene.

Early Mendelian genetics focused on very simple genetic traits which could be explained by a single gene. For example, a flower might appear in either orange or yellow form, with no gradation between the colors. By studying plants and the ways in which they mutated, early researchers were able to learn more about the gene which determined flower color. However, by the early twentieth century, people were well aware that most traits are far too complex to be determined by a single gene, and the idea of polygenic inheritance was born.

Early researchers learned about the genes determining flower color by studying plants and the ways they mutated.
Early researchers learned about the genes determining flower color by studying plants and the ways they mutated.

One easily understood example of polygenic inheritance is height. People are not just short or tall; they have a variety of heights which run along a spectrum. Furthermore, height is also influenced by environment; someone born with tall genes could become short due to malnutrition or illness, for example, while someone born with short genes could become tall through genetic therapy. Basic genetics obviously wouldn't be enough to explain the wide diversity of human heights, but polygenic inheritance shows how multiple genes in combination with a person's environment can influence someone's phenotype, or physical appearance.

Skin color is another example of polygenic inheritance, as are many congenital diseases. Because polygenic inheritance is so complex, it can be a very absorbing and frustrating field of study. Researchers may struggle to identify all of the genes which play a role in a particular phenotype, and to identify places where such genes can go wrong. However, once researchers do learn more about the circumstances which lead to the expression of particular traits, it can be a very rewarding experience.

In pleiotropy, on the other hand, one gene is responsible for multiple things. Several congenital syndromes are examples of pleiotropy, in which a flaw in one gene causes widespread problems for a person. For example, sickle cell anemia is a form of pleiotropy, caused by a distinctive mutation in one gene which leads to a host of symptoms. In addition to causing mutations, pleiotropy also occurs in perfectly normal genes, although researchers tend to use it to track and understand mutations in particular.

If an animal has a gene that affects the length and color of its fur, the gene is pleiotropic.
If an animal has a gene that affects the length and color of its fur, the gene is pleiotropic.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

You might also Like

Readers Also Love

Discussion Comments

anon281501

@anon144458: Yes.

@Anon150024: No (multiple alleles).

anon150024

Are blood types an example of Polygenic Inheritance?

anon144458

question: is eye color for humans polygenic inheritance?

anon132723

great page. this is very helpful. thanks to all of you.

anon84211

Thanks a lot.

anon79125

no no. Don't include more technical details. You have impossible-to-understand articles all over the internet to use. Leave one simple one for someone who just needs a summary.

anon78338

thanks a lot. But it's much more informal. Include more technical details.

anon76050

Thanks! This was very helpful for my biology project!

anon74251

it really helped me a lot.

anon65247

thanks! brief but concise explanation. Big help for me.

anon64031

so would the chromosomes of a polygenic inheritance be autosomes?

anon63582

Thanks.

anon62723

this helped me very much. thank you.

anon62638

so there are only three traits that a person has then? Like, hair, height, and eye color?

sorry I'm just trying to answer a bio question with graphs and I just needed to know if we only had three polygenic inherited traits.

anon58392

thank you. this really helped with my science homework.

anon57465

this did help with my bio assessment.

anon56871

thanks for this brief and informative article. it really took a confusing subject and made it simple!

anon55423

thank you! very helpful.

anon53484

Very helpful!

anon48824

fantastic page for my assignment on polygenic inheritance. thanks to all of you.

Post your comments
Login:
Forgot password?
Register: