Fact 1: Mutations that lead to cancer usually occur in genes that control the cell cycle.

Fact 2: Free radicals can mutate genes and eventually lead to cancer or cell death.

Given the two facts above, answer the question "What that eventually lead to cell death usually occur in genes that control the cell cycle?" with the following options: 
- free radicals
 - acetic acid
 - free cells
 - A Greek letter
 - Localized damage
 - massive damage
 - radical animals
 - free animals


 

 free radicals        