We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

In Genetics, What Is Penetrance?

By Jillian O Keeffe
Updated May 23, 2024
Our promise to you
InfoBloom is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At InfoBloom, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

In genetics, certain gene mutations are capable of causing disease. Sometimes, everybody with a mutation displays symptoms of that disease, and sometimes, only some of the people carrying the mutation display symptoms. The proportion of people who show symptoms from the mutation is called the penetrance of the gene.

If a person carries a gene that is associated with a medical condition, it doesn't necessarily mean that the gene will cause the illness. As well as the action of the gene, other parameters, such as environmental stresses and the coexistence of other, interactive genes, can alter the development of medical conditions. On the other hand, the presence of some genes means that the illness will always occur.

Complete penetrance is the scientific term for when the presence of a gene always results in disease. One example of complete penetrance is the condition neurofibromatosis type 1. This means that 100 percent of people who have the genetic mutation associated with the disease show its symptoms. Another example is a certain mutation of a particular gene called FGFR3, which always causes the carrier to have achondroplasia and show clinical signs of dwarfism.

Marfan Syndrome is another medical condition with complete penetrance. Although the presence of the mutated gene does result in clinically visible symptoms, the signs can vary widely in severity from person to person. More obvious cases have bone abnormalities or problems with the circulatory system, but mild cases may only display minor, almost unnoticeable signs, like long fingers and a tall stature.

Reduced or incomplete penetrance means that not all people with a genetic mutation develop signs of the associated disease. Some mutations have a high likelihood of symptoms, whereas others have a low penetrance. The reasons behind the absence of disease in some people, and the development of problems in other people, are not very well understood. Research into the involvement of coexisting genes in disease development, however, has found that, in some cases, other genes act as modifiers on the mutated gene and prevent the unhealthy trait from being expressed.

Incomplete penetrance refers to mutations that have less than 100 percent penetrance. One such example is a mutation of the BRCA1 gene, which is associated with breast cancer. This gene mutation means that about 80 percent of women with the mutation will develop breast cancer at some point in their lives, but 20 percent will not. Retinoblastoma, a cancer of the eye, also has a genetic cause, although the mutation does not always result in cancer.

InfoBloom is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Link to Sources
Discussion Comments
By ddljohn — On Dec 17, 2014

@SarahGen-- Yes, sort of. What you're talking about is an issue of expression and penetrance is too. Penetrance is whether someone who carries a disease causing gene expresses the disease. If an individual does not express the disease, it's called reduced penetrance.

On the other hand, people who do express the disease can also experience it to different degrees. This is also about how the disease is expressed in an individual.

By SarahGen — On Dec 16, 2014

Sometimes, the same exact gene mutation causes different diseases in different individuals? How can genetic diseases express differently like this? Does it have to do with penetrance?

By bear78 — On Dec 16, 2014

I think that penetrance genes are better than genetic mutations that don't always cause disease. In the former, since the mutation always causes disease, there is no chance of people not knowing that they carry it. So they can take this into account when family planning for example.

On the other hand, people carrying genetic mutations that don't always cause disease may not even know that they are carrying it. So they may have children and pass the mutation on to their children. And at some point in their lineage, the mutation will probably cause disease.

So in this regard, I think that it's better for a gene mutation to have penetrance so that people know what is going on with them. Of course, I realize that we have no say in the matter.

InfoBloom, in your inbox

Our latest articles, guides, and more, delivered daily.

InfoBloom, in your inbox

Our latest articles, guides, and more, delivered daily.