Question

it is a crucial that the process of mitosis is error free. This is because otherwise healthy cells can

Answer 1

If the process of mitosis is not error-free, then healthy cells can become cancer cells. 

Answer 2

They can become cancer cells otherwise. To prevent this, cells have checkpoints when they grow in Interphase (G1, S, G2). At these phases, cells are checked to see if they are healthy and ready to divide. If a cell is found with an error, they can go through apoptosis.