Final answer:
The inactivation of the tumor suppressor gene (TSG) depends on whether the phenotype is dominant or recessive. Dominant phenotypes can be caused by gain-of-function mutations in oncogenes, which do not require inactivation of the TSG. Recessive phenotypes are generally associated with loss-of-function mutations in DNA damage suppressor genes, which are recessive alleles.
Step-by-step explanation:
During cell fusion experiments, the inactivation of the tumor suppressor gene (TSG) depends on whether the phenotype is dominant or recessive. In the case of dominant phenotypes, the TSG is not necessarily inactivated. Dominant phenotypes can be caused by gain-of-function mutations in oncogenes, which do not require inactivation of the TSG. On the other hand, recessive phenotypes are generally associated with loss-of-function mutations in DNA damage suppressor genes, which are recessive alleles. These mutations may accumulate and lead to tumor formation.