What are proto-oncogenes?

Proto-oncogenes are normal genes that play a crucial role in promoting cell division and regulating cellular growth and differentiation. When functioning properly, they help to drive the process of cell cycle progression and ensure that cells divide in a controlled manner, contributing to normal development and tissue maintenance.

However, when these proto-oncogenes undergo mutations or become overexpressed due to various factors, they can transform into oncogenes, leading to uncontrolled cell division and potentially contributing to the development of cancer. This aberrant activity is typically the result of changes that enhance their function or increase their expression, thus tipping the balance towards excessive cell proliferation.

In contrast, the other options describe different gene functions that are not characteristic of proto-oncogenes. Some genes do indeed inhibit cell division or promote apoptosis, but those would be classified as tumor suppressors or related to different pathways in cell regulation, so they do not align with the role of proto-oncogenes in cell growth and division.