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What is a use of ΔCt and ΔΔCt in qRT PCR? - (Aug/27/2012 )

Guys i want to start qRT-PCR using absolute quantification method to find the exact targets present in my Sample. In that i did not clear about ΔCt and ΔΔCt? Please answer me the use of ΔCt and ΔΔCt in qRT PCR?

-Chinnaraja C-

If you are doing Realtime PCR to check Expression level. You always need to normalize your test reading with something that constitutively express in cells. Here may be GAPDH or beta- actin as constitutively expressing genes. So You have target now and GAPDH. You determine how much is expression level of your Target gene increased or decreased during experiment. Here it suggest that you have to have control where don't influence its expression level.

So here is how much your gene expressed,

Fold Change = 2-Δ(ΔCT)

where ΔCT = CT, target - CT, GAPDH
and Δ(ΔCT) = ΔCT, stimulated - ΔCT, control


Check this link


Thank you friends...Its really informative...

-Chinnaraja C-

In absolute quantification you use neither of these. You calculate it from the standard curve (can be found as standard curve method).