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qPCR result interpretation - when your 'relative' is 0?? - (Oct/24/2011 )

I am not sure how to express my qPCR results.

In short, I have 2 samples. The first is a negative control, so technically its value is zero (a gene that should not be expressed). The second is essentially a positive control, and thus should be expressed.

qPCR results - Ct(SMD)
2 repeats*
<*>NC: n/a, 38
<*>PC: 35, 34

To interpret my results in a graph, should I;

a. interpret the NC as 0 or n/a or ignore n/a and use the available data?

b. divide PC to NC in order to get relative amount?

Hope this explanation is clear..

Many Thanks.


Cts of 34-35 are already quite high. Do you know if this Ct range is still in your linear dynamic range of the assay? If not, you cannot quantify it. How did your non-template control look like, because your are also getting in your NC a signal in one replicate?


I'm not sure of the linear dynamic range (how can I obtain this information?) but my non-template control were as followed;

<*>NC: n/a, 38
<*>PC: 35, 34
<*>NRT:n/a, 38

So it appears that there is some increase in gene expression upon stimulation (PC).

I realise that the Ct levels are high and may not be interpretable. However, I would like to know, for future reference, how to interpret results for these kind of situations.
As you said, should I ignore the signal for NC, when theoretically there should be no signal at all? Should I assign the value as '0', or is 'n/a' more correct?