Genetic terminology can be quite complicated and difficult to understand. One of the many areas of training a genetic counselor undertakes during school is how to explain genetic terminology in ways everyone can understand. In addition to the terminology being difficult, often there are multiple terms for the same concept. For example, the terms allele, gene, and locus are all fairly comparable terms and refer to similar parts of our genetics. In addition, the term genetic predisposition is similar in meaning to the terms genetic condition or genetic mutation but each has different nuances.
The term genetic predisposition means that a person has an increased risk of developing a particular disease based on their genetic makeup. If someone has a genetic predisposition to a disease, they are not guaranteed to have the disease, but they do have an increased risk throughout their life of developing the disease. In other words, genetic predisposition means a person has genetic changes that can contribute to developing a disease throughout their life, but those genetic changes do not directly cause that disease. This is different from a person who has a genetic condition, which means they have a disease throughout their lifetime and their symptoms are caused by the gene mutation.
There are several categories of diseases and how they develop based on etiology that can fall into the category of genetic predisposition. To name a few:
Single Gene Disorders: There are many genetic conditions that are caused by one gene mutation and inherited in a family. Some genetic conditions require two copies of a gene to be mutated in order to manifest, other genetic conditions manifest symptoms with only one copy of the gene mutated. The majority of gene mutations that cause a genetic predisposition to a disease require only one copy of a gene to be mutated. For example, inherited cancer syndromes cause a lifetime increased risk of cancer. There are also some gene mutations that cause a lifetime increased risk of heart disease.
Multi-factorial Conditions: These types of diseases are more complicated than single gene disorders. Instead of being caused by one gene mutation, multi-factorial conditions are typically caused by a combination of genetic factors and environmental factors. We often cannot identify one gene mutation that would cause a multi-factorial condition. Instead, by taking a family history we can see that a person would have a genetic predisposition to a multi-factorial condition based on the number of family members in their family with the condition, ages of diagnosis, and manifested symptoms.
Chromosome Abnormalities: Sometimes portions of our chromosomes, which house all of our genetic instructions, can be deleted or duplicated, or even put in the wrong places within other chromosomes. More often than not, chromosome abnormalities show symptoms at birth and are not considered a genetic predisposition but rather a genetic condition. However, there are a few minor chromosome abnormalities that can predispose a person, often in reproduction, later in life.
For someone who has a genetic predisposition to a disease, there are important lifestyle and medical management steps they can take to help prevent or screen for disease. If you have questions regarding if you have a genetic predisposition to a certain disease and would like to discuss your concerns with a genetic counselor, please contact AT-GC to meet with a genetic counselor.