Answer:
variably expressive and incompletely penetrant
Step-by-step explanation:
Polydactyly is a genetic disorder characterized by limb malformation (i.e., supernumerary digits). Polydactyly is a genetically complex trait influenced by different factors, including, among others, epigenetic factors, environmental factors, regulatory genomic sequences (enhancers and/or suppressors), etc. The variable expressivity of this trait is caused by the combination of these factors. Incomplete penetrance refers to the fact that the trait is expressed in only some individuals having the genetic predisposition for this condition.