The human genome has roughly 4 billion base pairs. What would happen if human DNA manufacturing proofreading machinery erred at a rate of 1 in a

 The human genome has roughly 4 billion base pairs. What would happen if human DNA manufacturing & proofreading machinery erred at a rate of 1 in a million? What about 1 in a billion? 1 in a trillion? What number must be reached to be compatible with life & yet not so cumbersome such that the cell has no energy left for any other growth or manufacturing?