Autosomal Recessive Inheritance

Autosomal recessive inheritance occurs when an individual inherits two copies (double dose) of a mutated gene. In this scenario, the body cannot produce any normal protein. For example, those who carry only one copy of the mutated gene are considered carriers. Carriers do not show symptoms of the disease but can pass the gene to their children. Examples of autosomal recessive diseases include cystic fibrosis, sickle cell anemia, and Tay-Sachs disease.

When two carriers have a child, there is a: 

• 25% chance the child inherits two normal gene copies, not developing the disease or being a carrier. 
• 50% chance the child becomes a carrier like the parents. 
• 25% chance the child inherits two affected gene copies, potentially showing symptoms of the condition. 

This means that typically, both parents need to be carriers for their child to inherit the condition, highlighting the recessive nature of the gene. 

Autosomal Dominant Inheritance

Autosomal dominant inheritance means that inheriting just one altered gene copy from a parent is enough to disrupt the normal function of a protein, leading to the symptoms of the disease, as seen in conditions like Huntington’s disease. Unlike recessive conditions, where both parents must carry the altered gene, with dominant inheritance, having one copy is sufficient to potentially show symptoms. For someone affected by an autosomal dominant condition, each child they have, regardless of their partner’s gene status, has a 50/50 chance of inheriting the altered gene. 

Huntington’s disease, passed down through autosomal dominant inheritance, underscores the importance of understanding family history and genetic risks when planning for a family. While some hereditary conditions follow clear inheritance patterns, there are additional factors influencing the development and severity of Huntington’s disease beyond the gene alone.