How does a proto-oncogene differ from an oncogene?

• A. Proto-oncogenes code for proteins that regulate expression of structural genes; oncogenes code for nucleic acids involved in cell division.
• B. Proto-oncogenes control normal cell division; oncogenes contribute to the development of cancer.
• C. When oncogenes become damaged, they become proto-oncogenes.
• D. Oncogenes activate tumor suppressor genes; proto-oncogenes repress tumor suppressor genes.
• E. Proto-oncogenes cause cells to self-destruct when damaged; oncogenes cause damaged cells to repair themselves.

Answer: (B)

Verified step by step guidance

1. Begin by understanding the definitions: Proto-oncogenes are normal genes that play a role in cell growth and division. Oncogenes are mutated or overexpressed versions of proto-oncogenes that can lead to cancer.
2. Recognize the function of proto-oncogenes: They code for proteins that help regulate normal cell division and growth. These proteins are essential for maintaining healthy cellular functions.
3. Understand the transformation process: When proto-oncogenes undergo mutations or are expressed at high levels, they can become oncogenes. This transformation disrupts normal cell regulation and can lead to uncontrolled cell division, contributing to cancer development.
4. Clarify the role of oncogenes: Oncogenes can lead to the activation of pathways that promote cell proliferation and survival, bypassing normal regulatory mechanisms. They do not activate tumor suppressor genes; rather, they can inhibit their function.
5. Differentiate between the effects on cell behavior: Proto-oncogenes do not cause cells to self-destruct; instead, they support normal cell function. Oncogenes, when mutated, can prevent damaged cells from undergoing apoptosis (self-destruction), allowing them to survive and potentially become cancerous.