How do oncogenes differ from proto-oncogenes?

Oncogenes are mutated or overexpressed versions of proto-oncogenes, which normally help regulate cell growth and division in a controlled manner. When proto-oncogenes are altered, they can become oncogenes that drive the uncontrolled proliferation of cells, leading to cancer. This transformation often occurs through mutations in the DNA that increase the activity of the proto-oncogene or through amplification, which results in overproduction of the corresponding protein.

The correct choice highlights that oncogenes can cause either the overexpression or mutation of proto-oncogenes, fundamentally changing their role in the cell. This pathogenic transformation plays a central role in tumorigenesis, as the regulators of cell growth are turned into promoters of unrestrained proliferation when mutated or overactive.

In contrast, the other options misrepresent the functional roles of oncogenes and proto-oncogenes. Since oncogenes are a result of mutations from proto-oncogenes, the concept of oncogenes promoting normal cell growth or inhibiting the cell cycle contradicts their actual function, which is to promote uncontrolled growth. Similarly, the notion that proto-oncogenes can transform into tumor suppressor genes is incorrect; proto-oncogenes and tumor suppress