What would happen if we add only one primer, say forward primer, to PCR?PCR Amplification

(Image Credits: Wikipedia) As it is clear from the image that we need both forward and reverse primers to get it working (Unless we have a sequence such that a single primer can work as both forward and reverse). I have read online here that including a single primer will result in linear amplification but I think there should be no amplification at all. Can you help me resolve my doubt?


closed as off-topic by James, kmm, March Ho, Chris Jul 24 '16 at 6:51

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  • $\begingroup$ Welcome to Biology Stack Exchange. However you need to do a little more research before asking questions like this one. Guesses are not enough. There are many resources on the web which describe PCR, and if you read them carefully — especially the diagrams — it will be obvious why two primers are needed. This is fundamental. Look at the diagram here, for example. $\endgroup$ – David Jul 23 '16 at 11:22
  • $\begingroup$ Hi @David! I have researched online before asking the question and also looked at the link you sent. My apologies as I didn't make it clear. I will edit the question to make it clear. $\endgroup$ – Biginer Jul 23 '16 at 13:12
  • $\begingroup$ PCR with a single primer is similar to DNA sequencing, except you don't have labeled terminal monomers to stop the reaction. $\endgroup$ – user137 Jul 24 '16 at 13:15
  • $\begingroup$ I'm not sure why it has been put on hold as off-topic. It is not a question I'm getting grades for. I am not a student anymore. I study biology because of my interest. I was wondering what would happen if there is only one primer and I think theoretically there should be no amplification. I find contradictory views online and just wanted to know if I'm missing something. $\endgroup$ – Biginer Jul 24 '16 at 14:00

I think the following should happen:PCR amplification with one primer There would be no amplification but we will get n copies of single stranded DNA after n cycles and the only double stranded DNA with started with but with a new complementary strand.


Using 1 primer will results in amplifying the original sequence in each cycle in a linear fashion: the primer will guide a single run of the polymerase. In opposed to the "chain reaction" in PCR which is exponential. Therefore, with one primer you linear amplification of say x40 times the original number of molecules you started with, whie with two primers you get exponential (~240) amplification. You right that with one primer, the amplification is neglectable, almost invisible.

  • $\begingroup$ I don't think there would be no amplification at all. What will be present after 40 cycles are 40 single stranded DNAs and only one DNA of interest. Can you explain how would there be 40 more molecules? $\endgroup$ – Biginer Jul 23 '16 at 14:53

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