Virginia Commonwealth University

VCU Massey Cancer Center

Multi-factorial inheritance

Multi-factorial inheritance means that many factors are involved in causing a health problem. The factors are usually both genetic and environmental, where a combination of genes from both parents in addition to environmental factors produce the trait or condition. Multi-factorial traits do recur in families because they are partly caused by genes and shared environmental factors. The chance for a multi-factorial trait or condition to happen to you depends upon how closely you are related to the family member with the trait. For example, the risk is higher if your parent or sibling has the trait or disease than if your first cousin has the trait or disease. Family members share a certain percentage of genes in common, depending upon their relationship. For example:

Degrees of relationship

Percentage of genes in common

Example

First-degree relative  50 percent  Parents, children, siblings 
Second-degree relative  25 percent  Aunts, uncles, nieces, nephews, grandparents 
Third-degree relative  12.5 percent  First cousins 

An example of a multi-factorial trait is height. Some people may be exceptionally short or exceptionally tall, often due to an alteration (mutation) in a single gene that has a major effect on height. However, most of the time, a child’s height is similar to or somewhere in between the parents’ height. Some cancers cluster in families as the result of a combination of genetic and shared environmental factors (multi-factorial influences). In such cases, generally speaking, the closer in relation a family member with cancer is to you (i.e., the more genes you share in common), the higher your chance also to develop cancer. In other words, it is more significant for your personal health if one of your parents or siblings develops cancer (or other disease), than if your second cousin develops the disease.