Bannayan-Riley-Ruvalcaba Syndrome
A Guide for patients and their families
How is it inherited
Sarah Burton, UI Health Care
Joy Larsen Haidle, MS, CGC, UI Health Care
Heather Hampel, MS, CGC, Ohio State University
Peer Review Status: Internally reviewed by the authors
First Published: 2002
Last Revised: 2002
How is Bannayan-Riley-Ruvalcaba Syndrome Inherited?
Bannayan-Riley-Ruvalcaba can be inherited or passed from an affected parent to a child. While this is a common way to receive a gene change, it is not the only way. New gene changes (de novo) can occur by chance in the sperm or egg that formed an individual. A new gene change is not the result of something that did or did not happen in pregnancy nor can it be prevented. This type of change can result in a condition occurring in someone who does not have family history of that condition.
Bannayan-Riley-Ruvalcaba syndrome is described as having an autosomal dominant pattern of inheritance. Autosomal is a term used to describe genes that are passed equally from parent to child with no preference between males and females. Dominant describes a gene change that will cause the features of a condition to be present when one copy of the gene has been changed. This means that each child with an affected parent has a 50 percent chance of inheriting the gene change and developing Bannayan-Riley-Ruvalcaba syndrome. Likewise they have a 50 percent chance of not inheriting the gene change and not developing the syndrome.
This diagram shows how one gene from each parent is passed to a child. In the case above the father has one working gene, indicated by the lower case letter n, and one gene with a change, indicated by the capital letter N. The mother has two copies of normal genes. There are four possibilities of gene combinations for the child. Each child has a 50 percent chance of inheriting the changed gene (N), regardless of the sex of the child.
An evaluation of your family history can determine if a pattern exists. A family tree or a pedigree is a diagram of the members of your extended family. Below is a pedigree that demonstrates the pattern of autosomal dominant inheritance within a family.
This pedigree tells us several things about this family.
- Sue and Tom have three children, two of whom are affected. Since Sue was affected, each of her children had a 50 percent chance for developing Bannayan-Riley-Ruvalcaba syndrome, but only Joe and Jim actually inherited the gene change.
Sara did not inherit the gene change and has not developed Bannayan-Riley-Ruvalcaba syndrome. She cannot pass this gene on to her children, nor will they develop Bannayan-Riley-Ruvalcaba syndrome. Joe has one daughter who had a 50 percent chance of inheriting the gene change and developing Bannayan-Riley-Ruvalcaba syndrome. Jen did not inherit the change, will not develop BRR, and cannot pass the gene change to her children. Kay and Jim have two children, one inherited the gene change. Tim inherited the gene change and he now has a 50 percent chance of passing this gene on to his children. Lori did not inherit the change and can not pass the gene to her children.
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