Question

Using the gas pedal and brake analogies, explain the impact on the cell cycle of a proto-oncogene versus an oncogene.

Answer 1

In this context, the example of a car is very popular and simple to understand. Remember that cancer cells are produced by specific mutations in two type of genes: tumor suppressor and oncogenes. Tumor suppressor are genes that regulate the cell cycle, it works as a brake pedal in a car. An oncogene acts in the opposite way, it promotes the cell cycle and cell proliferation so it works like the accelerator pedal (gas pedal) in a car.

If a mutation affects the tumor suppressor genes, the break pedal wont be functional and the cell will keep dividing uncontrollably, just as a car when it lose its brake pedal. Now, in the case of oncogenes, the mutation enhance their expression in cancer cells. So, the accelerator will be always pushed in our car. If you keep pushing the accelerator, the car wont stop. In a cell, if oncogenes are overexpressed, the cell will keep dividing until form a tumor.