A mutation that causes loss of certain receptors can contribute to tumor formation by disrupting signaling that regulates what?

• A. Photosynthesis
• B. Immune response
• C. Oxygen transport
• D. Cell growth and apoptosis

Answer: (D)

Signals that tell a cell when to grow or die regulate how tissues develop and maintain their size. Receptors on the cell surface detect external cues and relay messages through pathways that promote cell division or trigger programmed cell death (apoptosis). If a mutation causes loss of these receptors, the cell loses essential information about when to grow and when to die. This can tilt the balance toward continued proliferation or survival of damaged cells, enabling tumor formation. The other processes mentioned aren’t directly about the signaling that tightly controls growth and apoptosis, so they don’t explain how receptor loss promotes tumors as well.