ID #2431

Why do more mutations occur in vitro than in vivo?

If you're referencing the last slide of lecture 22, that slide is referring to E. coli DNA  polymerase in vitro.  However, that is just the portion that does DNA synthesis; it is possible to have a DNA polymerase that lacks the proofreading activity but still synthesizes DNA.  Without the proofreading, the polymerase will most likely make 100x more errors.   
And the mismatch repair enzymes are a separate system that would not be included in the same test tube as the polymerase unless they were specifically added, which accounts for another 100 errors.  
So in the test tube, when you multiply the errors from no proofreading with the errors from no mismatch repair (100 times 100) you end up with 10,000 times more errors.  

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