In my bio class, we learned that you can use restriction enzyme or PCR to linearize a plasmid. Linearizing by restriction enzyme seemed visual and intuitive but how do one linearize a vector using PCR? I know how PCR works(at least I believe I do), since I watched couple of videos on YouTube explaining them.

But it is not connecting to me how PCR can be used to linearize a "circular" DNA. I have seen videos where a straight double stranded DNA was separated into single strands and using PCR to produce multiple copies with appropriate primers.

But if a plasmid, the circular DNA is not "straight" or linearized in the first place how do you perform PCR on it? Because if they are in a circular state during PCR the strand would never separate in to linear strands. Wouldn't you just have two sperated strands that are circular? E.g a small ring of single strand DNA and a bigger ring of single strand DNA. They are still in circular state after the strands split from each other. Please correct me if I am spitting out nonsense. I just don't see the visual here.


If you use PCR, the products from the reaction will be linear pieces of DNA. Yes, you'll have two templates that are circular after the first denaturation, but when you anneal the primers and perform elongation you'll be making linear fragments. The exponential nature of PCR means that these linear fragments will far exceed the template after several cycles.

PCR can also be tuned to be selective for shorter fragments. If you use the proper protocol for PCR of the entire plasmid, your PCR products will be a complete copy of the plasmid that is linear.


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