Why is careful regulation of the cell cycle important?

During the cell cycle, cells are undergoing a replication process which passes on the genome of one cell to another cell that is genetically similar. In theory this relay of DNA should be perfect, but in practice mutations, or changes in DNA sequences, may occur--and when the mutated cell undergoes mitosis, it will then send its changed, imperfect DNA to its daughter cell. The result of mutations may be detrimental to the organism, helpful, or show no effect phenotypically. It's imperative that the cell cycle is highly regulated because if mutations arise in consequential regions of DNA, the organism may fail. For example, if the gene that codes for hemoglobin, the molecule which delivers oxygen around your body, mutates and no longer functions, biological processes which require oxygen--electron transport chains, among others--will fault, and the organism will die. With out the check points embedded into varying phases of cell duplications, unneeded mutations will accumulate--therefore with out a highly regulated cell cycle, genomes can develop freely ultimately damaging the organism as a whole.