Richard Rohan rrohan at
Fri Oct 13 23:22:08 EST 1995

pnh at (Paul N Hengen) wrote:

>I'm confused about something. More than a few times I've seen people refer to a
>separately expressed gene used in quantitative RT-PCR as an `internal' control.
>I thought this was considered an `external' control. Can someone clarify what
>`internal' and `external' controls are with this technique?

I consider any transcript made by the target cell (eg rRNA, actin,
cyclophilin, RPS2) to be an internal standard.  Any artificial DNA or RNA (eg
a mimic or an in vitro transcribed and quantified RNA), which is used to spike
the sample, is an external standard.


Rich Rohan

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