Slide 3 showed that cultured cells can be classified as being immortalized or transformed (on their way to becoming fully metastatic). Viral oncogenes can have specific functions that make cells in culture immortalized or transformed, and thus they can be classified as having either one activity or the other. Adenovirus E1A, for example, has immortalizing activity. Retroviral oncogenes can also be classified in this fashion. For example, the viral myc gene is immortalizing and the viral ras gene is transforming.