Suppose that a certain gene functions to enforce a checkpoint on the cell cycle. a mutation causing the loss of this gene's function would be most likely to cause a person to
a. develop an extra limb
b. have cancer immediately
c. be more likely to have cancer at some point in his/her life
d. lose the capability to produce gametes
e. be extra protected from ever getting cancer

The correct answer is C. be more likely to have cancer at some point in his/her life.

Explanation:

Cell cycle checkpoints are controlled by different proteins which are coded by different genes. They are important in cell cycle regulation and stops cell cycle immediately if they find any problem in the cell like mutation.

The cell cycle will not be continued if the problem does not solve and cell death will occur which prevents cancer by preventing the mutation to spread into new cells.  

Therefore if a mutation occurs in certain genes that enforce a checkpoint on the cell cycle then the mutated gene will pass in new cells and the mutated cells will grow uncontrollably due to no checkpoints so the person will probably have cancer at some point in his or her life.