Hi Sharon,

We  use carrier DNA to improve PCR sensitivity especially if the extracted DNA is fragmented. The commercially available carrier DNA is dissolved using nuclease free water and then added to the PCR reaction. it is useful for low concentrations and fragmented DNA samples.

Thanks - I think this is the case for us. We have low quantities of bacterial DNA and the carrier vastly improves sensitivity. 

I have no experience of this but I wonder if this is due to absorption of the small amount of dna onto the plastic of the tube taking it out of the reaction mechanism but by adding carrier rna or dna the absorption sites are saturated with carrier dna leaving all of the target dna in solution and available for amplification

Hi Paul,

This is what we think too. It may act as a sort of blocking agent, like milk powder in Western blotting. I don't know if it may also block potential unspecific primer binding sites too, and also increase sensitivity that way. 

When you have extreme small amounts of DNA, a few molecules of any contaminating nucleases will decrease the sensitivity of your assay (or the storage stability of the samples). The addition of carrier DNA will make the nucleases busy with digestion this external DNA and thus indirectly save your precious sample DNA from digestion.   

HI Fawaz and Sharon,

How much of carrier DNA did you add to each PCR reaction (e.g. 50 or 100ul PCR reaction)?  We have customers having trouble for PCR with very small amount template DNA.  Thanks in advance! 

Include 1 - 10 ng foreign DNA in each PCR tube

Hi Michelle,

It depends on the DNA concentration.

In my research I used to add 5 Microliters from the carrier DNA aliquot in 50 microliters reaction. 

Einar and Fawaz, Thanks!

very interesting. evolutionary competition on a level of the dissolved dna, who struggles for a food allowing amplification

Einar and Fawaz - thanks for answering. I was away for business, only just noticed the question!