What does it mean when a disease is recessive?

In genetics, a recessive disease or trait is one that is only expressed when an individual carries two copies of the gene that causes the disease. This is in contrast to a dominant disease or trait, which is expressed when an individual carries only one copy of the disease-causing gene.

Recessive diseases are typically inherited from both parents, who each carry one copy of the gene. When two carriers of a recessive gene have children, each child has a 25% chance of inheriting two copies of the gene and thus expressing the disease.

Some common examples of recessive diseases include:

* Cystic fibrosis

* Sickle cell anemia

* Tay-Sachs disease

* Phenylketonuria (PKU)

* Albinism

Recessive diseases can be challenging to diagnose, as they may not be apparent in individuals who carry only one copy of the disease-causing gene. However, genetic testing can be used to identify carriers and to determine if a child is at risk of developing a recessive disease.

Treatment for recessive diseases can vary depending on the disease, but may include medications, surgeries, and lifestyle changes.