Mendelian disorders

Mendelian disorders are genetic diseases resulting from abnormalities in a single gene. They are named after the Austrian monk and scientist, Gregor Mendel, who is credited with the discovery of the fundamental laws of heredity. These disorders are also referred to as monogenic disorders, which means they are caused by a mutation in a single gene. Mendelian disorders can be inherited in a variety of ways and range in severity from mild to deadly. Common examples of Mendelian disorders include cystic fibrosis, Huntington’s disease, sickle-cell anemia, Marfan syndrome, and Tay-Sachs disease. The inheritance patterns of Mendelian disorders are determined by the type of gene involved. Autosomal recessive disorders, such as cystic fibrosis, require both copies of the gene to have the mutation in order for the disease to be expressed. Autosomal dominant disorders, such as Huntington’s disease, require only one copy of the mutated gene to be present for the disease to be expressed. X-linked recessive disorders, such as Duchenne muscular dystrophy, require only one mutated gene on the X chromosome for the disease to be expressed.