UNDERSTANDING INHERITANCE PATTERNS
Many factors including ethnicity, gender, and family history affect your risk of having a genetic disorder and potentially passing it on to your children. When the mutation is recessive, there is a 25% of having a child with an inherited disease. This risk increase to 50% with dominant mutations. Learn more about how mutations are inherited and how they can cause disease below.
FACTS ABOUT INHERITED DISORDERS
- Autosomal conditions are caused by gene mutations located on autosomal chromosomes.
- In autosomal recessive disorders, both copies of the gene must be mutated in order to cause a disease.
- In an autosomal dominant inheritance, one mutated copy of the gene is sufficient to cause the disease.
- An individual who has a mutation in only one copy of a gene is considered a carrier.
- Carriers are typically asymptomatic, but they have a risk of passing the mutated gene to their children.
- Although these disorders are relatively rare, an average person may be a carrier for at least eight significantly detrimental disorders.
- When both parents are carriers, there is a 25% chance that they will have an affected child; this couple has a 50% of having a child who is also a carrier for the disease.
X-LINKED CONDITIONS
X-linked disorders are so named because they are caused by genes located on the X chromosome. Females have two copies of the X chromosome, while males have one X and one Y chromosome. The single copy of the X chromosome puts males at an increased risk of having X-linked disorders. A carrier mother has a 50% chance of passing on her mutated copy of the gene to her children. Carrier females typically exhibit mild symptoms or none at all because they still possess one healthy copy on their other X chromosome. However, all sons who inherit the mutated gene will be affected with the disease because they have no healthy copies to compensate.
CANCER
The genetics of cancer is a complicated story. Through widespread efforts of cancer researchers around the world, our understanding of the role of genetics in cancer has developed tremendously. It is important to understand that cancer is a multi-factorial disease, where both genetic and environmental factors contribute to risk on an individual basis. A person who inherits a cancer-risk gene does not necessarily show symptoms or ever develop cancer, but they can still pass this gene to their children. Although not all forms of cancer are inherited, studies have identified over 50 hereditary cancer syndromes with strong evidence for a genetic link.
ETHNICITY AND GENETIC DISEASES
Some genetic diseases are more common in particular ethnic groups compared to the general population. This is because people in the same ethnic group share some genetic information inherited from common ancestors. Common examples include:
- Ashkenazi Jewish – Tay-Sachs Disease, Cystic Fibrosis
- African – Thalassemia, Sickle Cell Disease
- Asian Thalassemia
- Caucasian – Cystic Fibrosis
- Mediterranean – Thalassemia, Sickle Cell Disease
