Mutations

ID #2133

In my notes it first says "DNA replication is the most reliable" but then on the next page it says "Most mutations occur during DNA replication" (These are quotes directly from the ppt. notes, not my handwritten notes) ... the weekly review question (Question 3 from WR 7) was a T/F statement:" More mistakes are made during transcription than DNA replication. " I said false because I figured even if DNA replication makes fewer mistakes, it has the opportunity to make a larger number of mistakes because as the notes say "that's when huge amounts of DNA are synthesized"; therefore the quantity of mistakes made would be greater from replication. The statement in the weekly review question was true, however, so I am confused. Could you please explain the flaw in my thinking and also clarify what seems to be a contradiction in the lecture notes?


DNA replication is a more reliable process than either transcription or translation because there is proofreading and mismatch repair during replication. DNA replication needs to be reliable because mutations in DNA affect the viability of an organism. The next page of the notes does say that most mutations occur during DNA replication, but I think that is saying that of mutations that occur to DNA, the vast majority occurs during replication. As you correctly point out, since so much DNA is synthesized during replication it would be more likely for mistakes to occur during that process. When comparing replication and transcription, there are going to be more mistakes during transcription because there is no proofreading and any mistakes that RNA Polymerase makes will not be caught.

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