Monogenic disorders are the consequence of a single defective autosomal gene. These disorders can be broadly classified into autosomal dominant, autosomal recessive, X-linked, and Y-linked disorders, based on the location and inheritance pattern of the defective gene. In some disorders, the condition results from a sole known mutation of a single gene, but more commonly from a variety of different possible mutations to a single gene result in a similar phenotype. Often, monogenic disorders are caused by either the failure to produce an important protein, such as a transmembrane protein or enzyme, or the production of a defective version of such a protein. Examples of single-gene disorders include thalassemias, sickle cell disease, galactosemia, phenylketonuria, cystic fibrosis, polycystic kidney disease, and Friedrich’s ataxia.

By their nature, individuals ...