Final answer:
Oncogenes, originally normal 'proto-oncogenes,' are the specialized copies of DNA that, when mutated, overexpress growth factors leading to cancer. Tumor suppressor genes, on the other hand, are often inactivated in cancer, contributing to uncontrolled cell growth.
Step-by-step explanation:
The specialized copies of DNA that code for growth factors contributing to neoplasia are known as oncogenes. Oncogenes are originally normal genes, referred to as proto-oncogenes, which when mutated, can lead to the overexpression of growth factors or proteins that promote uncontrolled cell proliferation characteristic of cancer cells. In contrast to oncogenes, tumor suppressor genes act to inhibit cell division and promote the repair of DNA damage, thus preventing cancer. However, when these genes are mutated or inactivated, their ability to suppress tumor growth is lost, adding to the potential for cancer development.
It's essential to understand that cancer typically results from multiple genetic changes that include the activation of oncogenes and the inactivation of tumor suppressor genes. This process leads to cells dividing uncontrollably—a hallmark of cancer. Specifically, the neoplastic transformation often requires the action of both classes of genes, highlighting the complexity of cancer as a disease of the cell cycle regulation.