GAPDH PCR: DNA vs. RNA...

[Roland Hübner]

Dear friends,

 I checked a DNA sample for amplification potential by PCR with GAPDH
primer pair... This primer pair spans 
intron "H" [for 4205-4225; rev 4742-4761] and is frequently used to
control for DNA contamination when setting
up RT-PCRs [RNA gives 450bp whereas DNA gives 550bp]...

 I am puzzled because I observe _ONLY_  _450bp_ in this extract...  The
DNA was extracted from cell line SVEC 
(SV40 transformed endothelial cells)... Extract on gel shows neat HMW band
and no obvious RNA contamination; this was PCR with Taq polymerase and
manual hot start...

 Can an intron get "lost" from entire genome?

Kind regards,
 Roland