is an improperly regulated cell cycle. name two reasons why cells can form causes uncontrolled cell division at the genetic level? the video clip. at the cellular level in this example, explain what occurs if the apc gene is mutated.26.normally, proto-oncogenes stimulate the cell cycle. what do mutated proto-oncogenes (i.e., oncogenes) cause?27.normally, tumor suppressor genes inhibit the cell cycle. what do mutated tumor suppressor genes cause?