Definition: Amphinucleus refers to a mutation in a human gamete that results in the fusion of two genes, leading to abnormal development or lack of function. This term often appears in medical literature where it describes an organism's inability to properly develop through normal development processes due to a genetic disorder or malformation. Definition: A mutant gene from one parent is fused with another gene present on the other parent, causing abnormalities. In humans, amphinucleus can manifest as certain types of cancer or defective cell growth.