DNA copying always introduces errors. Organisms have quite a few error correcting mechanisms to mitigate damage from bad copies.
Most DNA errors turn out to be inconsequential to the individual. If a cell suffers catastrophic errors during reproduction, it typically just dies. Same for embryos, they fail to develop and get reabsorbed. Errors during normal RNA transcription tend to encode an impossible or useless protein that usually does nothing. Malformed RNA can also get permanently stuck in the cellular machinery meant to decode it, but this also has no real effect. That transcriptase floats around uselessly until it's broken down and replaced. You've got a nearly infinite number of them.
DNA and all the machinery around it is surprisingly messy and imprecise. But it all keeps working anyway because organisms have billions or trillions of redundant copies of their DNA.
*take with a grain of salt, I last studied this stuff many years ago.
Most DNA errors turn out to be inconsequential to the individual. If a cell suffers catastrophic errors during reproduction, it typically just dies. Same for embryos, they fail to develop and get reabsorbed. Errors during normal RNA transcription tend to encode an impossible or useless protein that usually does nothing. Malformed RNA can also get permanently stuck in the cellular machinery meant to decode it, but this also has no real effect. That transcriptase floats around uselessly until it's broken down and replaced. You've got a nearly infinite number of them.
DNA and all the machinery around it is surprisingly messy and imprecise. But it all keeps working anyway because organisms have billions or trillions of redundant copies of their DNA.
*take with a grain of salt, I last studied this stuff many years ago.