Developmental Duplication (also referred to as polymelia) is a genetic condition that impacts specific lines of Angus and Angus-influenced cattle. Developmental Duplication (DD) has a simple recessive mode of inheritance. This means that animals must receive two copies of the deleterious allele, one from each parent, to be affected (designated as DDA). Animals that only receive one copy are "carriers" (designated as DDC) and transmit it to one-half of their offspring. Animals have no copies are "free" (designated as DDF) of the condition. It is important to note that DD carrier animals are physically indistinguishable from animals that are free of the condition. It is believed that many affected animals are absorbed in utero or aborted early in gestation. Those that do survive birth typically have additional limbs (usually extra front legs) originating from the neck or shoulder region.
Testing animals is the only practical way to identify DD free (DDF) and carrier animals (DDC).