Final answer:
The fusion of human and mouse cells produces heterokaryons and synkaryons, which are key to genetic research and chromosome mapping.
Step-by-step explanation:
The fusion of cultured human and mouse cells that produces cell lines useful in assigning a gene to a particular human chromosome involves the formation of heterokaryons and synkaryons. Heterokaryons are cells with multiple nuclei from different species, whereas synkaryons are cells where those nuclei have fused to form a single nucleus. This hybrid cell technique is instrumental in genetic research and assigning genes to specific chromosomes.