[sarah170194]

Hi
I have a question about the advantages of in vivo cloning.
My textbook says that an advantages of it over PCR is is that it does not copy contaminant DNA unlike PCR. However i thought PCR would not copy the contaminant DNA either as the primers will not be complementary to it.
Secondly it says PCR does not cut out specific genes-but i thought it could?

This is in the AQA A2 Nelson thornes textbook page 225.

I would be really greatful is someone could help me
Thanks

[NessEB]

(Original post by sarah170194)
Hi
However i thought PCR would not copy the contaminant DNA either as the primers will not be complementary to it.

There is still a chance the contaminant DNA will have complementary bases to the primers.

[NessEB]

(Original post by sarah170194)
Secondly it says PCR does not cut out specific genes-but i thought it could?
Thanks

PCR doesn't cut DNA into fragments, it amplifies specific genes by producing complementary DNA and as a result many copies of the required gene will be produced. Restriction endonuclease enzymes are used to cut out specific genes.

[sarah170194]

Sorry so are you saying that PCR just copies the whole bit on the DNA sequence you put into the thermocycler. I thought by having primers complementary to specific parts of the DNA you could make sure only certain parts of the DNA are amplified many times?

[Fizzeh]

You put in the DNA sequence that you want to be amplified. The primers are there (kind of like free nucleotides) to start the chains off, because nucleotides can only be joined by DNA polymerase to an existing chain.

(The primers are complimentary but not specific from what I understand. They just start the chains off; no choosing which DNA strands to annneal to. If there's a dodgy DNA sequence in there, the primer is going to join on the beginning of that contaminant DNA sequence regardless.)