Developmental duplication (DD) was described in 2013, prior to which the condition was believed to be the result of anomalies associated with foetal development or conjoined twins.
The condition most notably in its extreme form produces polymelia, the presence of extra limbs or part there of, typically from the shoulder or neck region. DD however is also associated with a number of other pathological phenotypes which result from the varied expression of the disease. The variation seen in the expression of DD means the condition can for some animals require minor surgery, whilst being lethal in others. The following are associated with DD;
DD is controlled by a simple recessive mutation.
Further readingAmerican Angus Association Flock and Herd