is a cell
that contains multiple, genetically different nuclei
. This can occur naturally, such as in the mycelium
during sexual reproduction, or artificially as formed by the experimental fusion of two genetically different cells. A medical example is a heterokaryon composed of nuclei from Hurler syndrome
and Hunter syndrome
. Both of these diseases result in problems in mucopolysaccharide metabolism however a heterokaryon of nuclei from both of these diseases exhibits normal mucopolysaccharide metabolism proving that the two syndromes affect different proteins and so can correct each other in the heterokaryon.