What is the main characteristic of a normal cellular gene that can become a proto-oncogene?

The main characteristic of a normal cellular gene that can become a proto-oncogene is that it requires alteration to become harmful. Proto-oncogenes are genes that, when mutated or abnormally expressed, have the potential to drive the transformation of normal cells into cancerous cells. These alterations can occur through various means, such as mutations, gene amplification, or chromosomal translocation.

In their normal state, proto-oncogenes play essential roles in normal cell functions, including cell growth and division. However, once they undergo changes, they can promote uncontrolled cell proliferation or inhibit apoptosis, which contributes to cancer development. Therefore, the key aspect is that these normal cellular genes need specific modifications to acquire their oncogenic potential.

This understanding highlights the nature of proto-oncogenes as vital components of normal cell biology that, under certain conditions, can lead to malignancies without being inherently harmful in their unaltered form.