In studying tumor cells, you isolate gene X that causes protein Q to become tyrosine phosphorylated (the addition of a phosphate group to a tyrosine). You isolate a homozygous null mutation in gene X and now find that protein Q is not tyrosine phosphorylated. Furthermore, the tumor cells are now behaving more like normal cells. That is, when protein Q is phosphorylated, it induces the cells to become more cancer-like.
If you concluded that Gene X is necessary, describe an experiment to test whether Gene X is sufficient. If you concluded that Gene X is sufficient, describe an experiment to test whether Gene X is necessary.