Fact 1: Cancer is a disease that occurs when the cell cycle is no longer regulated.

Fact 2: P16 is a regulator of the cell division cycle.

Given the two facts above, answer the question "P16 is an example of what type of thing that causes cancer when it stops functiong properly?" with the following options: 
- Toxins
 - edema
 - gene
 - ferns
 - CO 2
 - PDAs
 - HIV
 - albino


 

   gene      