What is the meaning of ΔΔCt in quantitative PCR and how is it calculated?

[Bio-student]

I'm a little confused about what the ΔΔCt value means and how its calculated - could anyone verify?

Also, I'm reading lecture notes that say "2^ΔΔCt assumes efficiency is 100%". I'm really baffled by this and would appreciate any guidance.

 

[Andy Resnick]

Yeesh... major jargon.

ΔΔCt seems to have to do with copy number, but the metric is 2^-ΔΔCt. I couldn't find a proper definition...

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1090581/
http://www.ncbi.nlm.nih.gov/pubmed/11846609

http://www.citeulike.org/user/wirawan/article/2519689

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1395339/